development of novel 3d woven reinforcements for high...

i

Development of Novel 3D Woven Reinforcements for High

Performance Applications

A thesis submitted by

Muhammad Umair

(14-NTU-7014)

In partial fulfilment of the requirement for the degree of

Doctor of Philosophy

In

Textile Engineering

Office of Graduate Studies & Research

Faculty of Engineering & Technology

NATIONAL TEXTILE UNIVERSITY, FAISALABAD

July 2018

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DEDICATION

This modest effort is dedicated to my

Family

&

Teachers

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CERTIFICATE OF APPROVAL

This is to certify that the research work presented in this thesis, titled “Development of

Novel 3D Woven Reinforcements for High Performance Applications” was conducted

by Mr. Muhammad Umair under the supervision of Dr. Yasir Nawab. No part of this thesis

has been submitted anywhere else for any other degree. This thesis is submitted to the

Office of Graduate Studies and Research (OGSR) in partial fulfilment of the requirements

for the degree of Doctor of Philosophy in Textile Engineering at National Textile

University, Faisalabad.

Student Name: Muhammad Umair_(14-NTU-7014), Signature: ___________________

Examination Committee:

a) External Examiner 1: Name Dr. Rizwan Hussain, Signature: ____________________

(Designation & Office address):

Director General, NESCOM, Headquarter, Islamabad.

b) External Examiner 2: Name Dr. Syed Zameer Ul Hassan, Signature: ______________

(Designation & Office address):

Associate Professor, Department of Textile Engineering, BUITEMS, Quetta.

c) Internal Examiner: Name Dr. Muhammad Zubair, Signature: ___________________

(Designation & Office address)

Assistant Professor, Weaving Department, National Textile University, Faisalabad.

Supervisor: Dr. Yasir Nawab ___________________

Co-supervisor(s): ___________________ ___________________

Signature: ___________________ ___________________

Director Graduate Programs

(FET):

Dr. Sheraz Ahmad______ _______________

Director Graduate Studies &

Research: Dr. Yasir Nawab_______ _______________

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Table of Content

1 Chapter 1: Context of study .........................................................................................4

1.1 Background ......................................................................................................... 4

1.2 Woven structures/reinforcements........................................................................ 5

1.2.1 Two dimensional (2D) woven structures ..................................................... 5

1.2.2 Three dimensional (3D) woven structures ................................................... 6

1.3 Solid 3D woven structures .................................................................................. 7

1.3.1 Orthogonal interlock structures.................................................................... 7

1.3.2 Angle interlock structures ............................................................................ 8

1.3.3 Hybrid interlock structures .......................................................................... 9

1.4 3D woven spacer structures ................................................................................ 9

1.5 Weave design of solid 3D woven multilayer interlock structures .................... 10

1.5.1 Weave design of orthogonal layer to layer interlock ................................. 10

1.5.2 Weave design of orthogonal through thickness interlock .......................... 12

1.5.3 Weave design of layer to layer angle interlock .......................................... 12

1.5.4 Weave design of through thickness angle interlock .................................. 14

1.6 Weave design of 3D woven spacer structure .................................................... 15

1.7 Polymer matrix .................................................................................................. 16

1.7.1 Epoxy resin ................................................................................................ 17

1.8 Fibre reinforced polymer composites (FRPC) .................................................. 21

1.9 Thermosetting composite fabrication techniques.............................................. 24

1.10 Application areas of fibre reinforced composites ...................................... 25

1.10.1 Composite characterization methods ..................................................... 26

1.11 Importance of fibre reinforced polymeric 3D woven composites ............. 28

1.12 Impact testing and failure modes of 3D woven solid composite structures

29

1.13 Factors affecting the energy absorption during damage of composite

structures 32

1.14 Compression, compression after impact (CAI) and other mechanical

behaviours of 3D woven solid composite structures .................................................. 34

1.15 Mechanical behaviour of 3D woven spacer composite structures ............. 37

1.16 Summary of literature ................................................................................ 38

1.17 Problem definition ..................................................................................... 39

1.18 Objectives .................................................................................................. 39

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2 Influence of interlocking patterns on mechanical performance of novel 3D woven

solid composites .................................................................................................................44

2.1 Introduction ....................................................................................................... 44

2.2 Experimental ..................................................................................................... 47

2.2.1 Reinforcement preparation......................................................................... 47

2.2.2 Composite fabrication ................................................................................ 49

2.2.3 Characterization ......................................................................................... 49

2.3 Results and discussion ...................................................................................... 50

2.3.1 Tensile Properties....................................................................................... 51

2.3.2 Impact properties ....................................................................................... 53

2.3.3 Flexural properties ..................................................................................... 54

2.3.4 Dynamic mechanical analysis (DMA) ....................................................... 57

2.4 Conclusions ....................................................................................................... 60

3 Effect of Z-binder yarn on the mechanical performance of hybrid 3D woven solid

composites..........................................................................................................................63

3.1 Introduction ....................................................................................................... 63

3.2 Materials and Methods ...................................................................................... 67

3.2.1 3D woven fabric structures ........................................................................ 67



3.3 Results and discussion ...................................................................................... 71

3.3.1 Tensile properties ....................................................................................... 71

3.3.2 Flexural properties ..................................................................................... 74

3.3.3 Short beam strength (SBS) properties........................................................ 77

3.3.4 Pendulum impact test results ..................................................................... 80

3.3.5 Drop weight impact.................................................................................... 82

3.3.6 Compression after impact (CAI) properties ............................................... 88

3.4 Conclusions ....................................................................................................... 90

4 Effect of pile height on compression/recovery properties of 3D woven spacer fabric

reinforced composites ........................................................................................................94

4.1 Introduction ....................................................................................................... 94

4.2 Materials and Methods ...................................................................................... 97

4.2.1 3D woven spacer fabric ............................................................................. 97



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4.3 Results and Discussion .................................................................................... 100

4.4 3D woven spacer fabric ................................................................................... 100

4.5 3D woven spacer fabric composites ................................................................ 100

4.5.1 Needle penetration resistance .................................................................. 100

4.5.2 Flexural properties ................................................................................... 102

4.5.3 Flat compression properties ..................................................................... 104

4.5.4 Low velocity impact ................................................................................ 107

4.5.5 Single cycle compression and recovery ................................................... 109

4.5.6 Cyclic compression and recovery ............................................................ 111

4.6 Conclusions ..................................................................................................... 116

5 General conclusions and future perspective ............................................................118

5.1 General conclusions ........................................................................................ 118

5.2 Future Perspective ........................................................................................... 122

6 References ................................................................................................................123

7 APPENDIX ..............................................................................................................144

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ACKNOWLEDGEMENT

I am grateful to my supervisor Dr. Yasir Nawab and co-supervisors Prof. Dr. Tanveer

Hussain and Dr. Syed Talha Ali Hamdani for their valuable guidance, suggestions,

inspiration and encouragement to complete this work. I am also thankful to Khubab Shaker,

Muhammad Ayub Asghar, Muhammad Kashif, Miss. Madeha Jabbar, Muhammad

Zeeshan, Dr. Mehmet Karahan (Turkey), Mumtaz Ali, Dr. Sheraz Ahmad (Director

Graduate Programs, FET) and all the laboratory staff of Department of Weaving. I would

like to extend my acknowledgements to Textile Composite Materials Research Group

(TCMRG) and National Center for Composite Materials (NC2M) of National Textile

University (NTU) for providing me their services whenever I needed.

Sincere thanks to all my colleagues and friends especially Dr. Muhammad Zubair,

Muhammad Umar Nazir, Muhammad Usman Javaid, Muhammad Zohaib Fazal, Haris

Ameer, Khurram Shahzad Akhtar, Miss. Shagufta Riaz, Shafiq Ur Rehman, Sharjeel Abid,

Muhammad Imran Khan, Muzzamal Hussain, Habib Awais, Hassan Iftekhar, Miss Adeela

Nasreen, Jahanzeb Akram, Muhammad Raza and Raja Muhammad Waseem for their

concern and ethical support.

I would also like to thank my beloved parents, my wife my sister and my colleagues who

enabled and motivated me to perform and successfully complete this research work.

Finally, I thank my God, for letting me through all the difficulties. I have experienced Your

guidance day by day. You are the one who let me finish my degree. I will keep on trusting

You for my future. Thank you, Lord.

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LIST OF ABBREVIATIONS

2D = Two dimensional

3D = Three dimensional

FRPC = Fiber reinforced polymer composite

O = Orthogonal interlock

A = Angle interlock

TT = Through thickness

LL = Layer to layer

OLL = Orthogonal layer to layer interlock

OTT = Orthogonal through thickness interlock

ALL = Layer to layer angle interlock

ATT = Through thickness angle interlock

Den = Denier

cm = Centimetre

mm = Millimetre

E/cm = Ends per centimetre

E/10cm = Ends per 10 centimetres

P/cm = Picks per centimetre

P/10cm = Picks per 10 centimetres

Vf% = Fiber volume percentage

Fab4 = 4 millimetres thick 3D woven spacer fabric



Comp4 = 4 millimetres thick 3D woven spacer fabric composite



ASTM = American Society for Testing and Materials

ISO = International Organizations for Standardization

J = Joule

Pmax = Maximum force

Ez = Compressive Modulus

δpmax = Compressometer deflection

N = Newton

MPa = Mega Pascal

GPa = Giga Pascal

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LIST OF APPENDIXES

APPENDIX 2.1 Weave design of 3D orthogonal layer to layer warp interlock………..144

APPENDIX 2.2 Weave design of 3D orthogonal layer to layer weft interlock… ……..145

APPENDIX 2.3 Weave design of 3D orthogonal layer to layer bidirectional interlock.146

APPENDIX 3.1 Weave design of 3D orthogonal layer to layer interlock, F1(OLL).….147

APPENDIX 3.2 Weave design of orthogonal through thickness interlock, F2(OTT)….148

APPENDIX 3.3 Weave design of layer to layer angle interlock, F3(ALL) ……………149

APPENDIX 3.4 Weave design of through thickness angle interlock, F4(ATT)……….150

APPENDIX 3.5 Weave design of hybrid 1 F5(H1) ………………………………..…..151

APPENDIX 3.6 Weave design of hybrid 2, F6(H2) …………………………….……..152

APPENDIX 3.7 Weave design of hybrid 3, F7(H3) …………………………………...153

APPENDIX 3.8 Reference for mean curve of results ..………………………………...154

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LIST OF FIGURES

Figure 1.1 Two dimensional (2D) woven structures ........................................................... 5

Figure 1.2 Three dimensional (3D) or multilayer woven structure ..................................... 6

Figure 1.3 Multilayer orthogonal through thickness interlock structure ............................. 7

Figure 1.4 Multilayer orthogonal layer to layer interlock structure ..................................... 7

Figure 1.5 Multilayer angle interlock through thickness structure ...................................... 8

Figure 1.6 Multilayer angle interlock layer to the layer structure ....................................... 8

Figure 1.7 Multilayer hybrid woven structure ..................................................................... 9

Figure 1.8 3D woven spacer structure ............................................................................... 10

Figure 1.9 Cross sectional view of two layers structure .................................................... 10

Figure 1.10 Cross sectional view of raiser stitching/interlocking of two layers ................ 11

Figure 1.11 Weave design of two-layer orthogonal layer to layer interlock with raiser

stitching/interlocking ......................................................................................................... 12

Figure 1.12 Weave design of six layers orthogonal though thickness structure ................ 12

Figure 1.13 Cross section of six layers layer to layer angle interlock structure ................ 13

Figure 1.14 Weave design of six layers layer to layer angle interlock structure ............... 13

Figure 1.15 Cross section of the three layered through thickness angle interlock structure

............................................................................................................................................ 14

Figure 1.16 Weave design of three layer through thickness angle interlock structure ...... 14

Figure 1.17 Cross sectional view of 3D woven spacer structure ....................................... 15

Figure 1.18 Weave design of 3D woven spacer structure ................................................. 16

Figure 1.19 Chemical formulation of different epoxy resins [52] ..................................... 18

Figure 1.20 Manufacturing cycle of the bisphenol A based epoxy resin [52] ................... 19

Figure 1.21 Mechanism of curing of epoxy resin with amine hardener [52] .................... 20

Figure 1.22 Manufacturing cycle of normal and green epoxy resin .................................. 20

Figure 1.23 Composite classification based on the matrix types ....................................... 22

Figure 1.24 Classification of natural fibres........................................................................ 23

Figure 1.25 Impact energy absorption of textile composite [88] ....................................... 30

Figure 1.26 Impact response of 3D and 2D woven composites (a) 3D orthogonally woven

(b) 2D Plain woven (arrows represent the incipient damage points in 3D and 2D woven

composites) [89]................................................................................................................. 31

Figure 1.27 Damage tolerance of different 2D and 3D composite structures [115] .......... 34

Figure 1.28 Compression after impact strength of 3D woven composites at different

energy levels [8] ................................................................................................................. 35

Figure 1.29 variation of flat compression properties with core height [142] .................... 38

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Figure 1.30 Flow chart of the study ................................................................................... 40

Figure 2.1 Cross sectional views of the orthogonal layer to layer (a) warp interlock, (b)

weft interlock and (c) schematic view of the bidirectional interlock................................. 48

Figure 2.2 Optical images showing cross section and fibre-matrix interface of the

orthogonal layer to layer interlock composites .................................................................. 50

Figure 2.3 Comparison of (a) tensile strength and (b) elongation at break (%) of the

composite structures........................................................................................................... 52

Figure 2.4 Comparison of the impact strength of the composite structures ...................... 53

Figure 2.5 Load versus elongation graph of the composite structures during flexural

testing ................................................................................................................................. 55

Figure 2.6 Comparison of (a) flexural strength and (b) flexural modulus of the composite

structures ............................................................................................................................ 56

Figure 2.7 Storage modulus as a function of temperature ................................................. 58

Figure 2.8 Loss modulus as a function of temperature ...................................................... 59

Figure 2.9 Tan delta as a function of temperature ............................................................. 60

Figure 3.1 Cross sectional views of F1 to F6 woven fabric structures and schematic view

of F7 woven fabric structure .............................................................................................. 68

Figure 3.2 Warp wise cross-sectional views of 3D woven composites ............................. 70

Figure 3.3 Testing fixtures of (a) tensile test (b) flexural test (c) short beam shear test (d)

pendulum impact test (e) drop weight impact test (f) compression after impact test ........ 70

Figure 3.4 Tensile stress versus extension (%) curves of 3D woven composites (a) warp

wise (b) weft wise .............................................................................................................. 71

Figure 3.5 Flexural stress versus deformation (%) curves of 3D woven composites (a)

warp wise (b) weft wise ..................................................................................................... 75

Figure 3.6 Deformation during interlaminar shear test ...................................................... 78

Figure 3.7 Force versus deformation curves of 3D woven composites (a) warp wise (b)

weft wise ............................................................................................................................ 78

Figure 3.8 Pendulum impact strength of 3D woven composites ....................................... 80

Figure 3.9 Force versus displacement curves of 3D woven composites (a) at 3 Joule

impact energy (b) at 6 Joule impact energy ....................................................................... 83

Figure 3.10 Force versus time curves of 3D woven composites (a) at 3 Joule impact

energy (b) at 6 Joule impact energy ................................................................................... 85

Figure 3.11 Work done versus time curves of 3D woven composites (a) at 3 Joule impact

energy (b) at 6 Joule impact energy ................................................................................... 86

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Figure 3.12 Energy absorbed (a) at 3 Joule impact energy (b) at 6 Joule impact energy by

3D woven composites ........................................................................................................ 87

Figure 3.13 Damage zones during (a) 3 Joule impact energy and (b) 6 Joule impact

energy tests......................................................................................................................... 88

Figure 3.14 CAI stress versus deformation (%) curves of 3D woven composites after (a) 3

Joule impact energy (b) 6 Joule impact energy ................................................................. 89

Figure 4.1 Yarn placement of 3D woven spacer fabric/reinforcement .............................. 97

Figure 4.2 Cross sectional view of 3D woven spacer fabric composites: (a) warp direction

(b) weft direction................................................................................................................ 99

Figure 4.3 (a) Setup of needle penetration test (b) Load versus penetration curves of 3D

woven spacer fabric composites ...................................................................................... 101

Figure 4.4 Flexural stress versus deformation (%) curves of composites: (a) Warp wise

(b) Weft wise.................................................................................................................... 102

Figure 4.5 (a) Experimental setup of flexural testing of composites (b) Fracture

morphologies.................................................................................................................... 103

Figure 4.6 (a) Compressive testing setup (b) Compressive stress versus deformation (%)

curves of 3D woven spacer fabric composites ................................................................. 105

Figure 4.7 Fracture morphologies of (a) Comp4, (b) Comp10 and (c) Comp20 ............. 105

Figure 4.8 Energy absorbed versus deformation curves of (a) Comp4, (b) Comp10 and (c)

Comp20 ............................................................................................................................ 107

Figure 4.9 (a) Experimental setup, (b) results of drop weight impact test and fracture

morphologies (c) on top side (d) cross section wise ........................................................ 108

Figure 4.10 Single cycle compression and recovery test setup ....................................... 109

Figure 4.11 Force versus sample thickness curves of (a) Comp4, (b) Comp10 and (c)

Comp20 ............................................................................................................................ 110

Figure 4.12 Strain versus time curves of (a) Comp4, (b) Comp10 and (c) Comp20 during

compression and recovery test ......................................................................................... 112

Figure 4.13 Hysteresis loop of (a) Comp4, (b) Comp10 and (c) Comp20 during

compression and recovery test ......................................................................................... 114

Figure 4.14 Graphs of work done during each cycle (a) force loading, (b) force unloading

and (c) work difference between both ............................................................................. 115

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LIST OF TABLES

Table 1.1 Comparison of properties of different resins ..................................................... 21

Table 1.2 Properties of different fibers .............................................................................. 24

Table 2.1 Notation for composite structures ...................................................................... 49

Table 2.2 Tensile properties of composite structures ........................................................ 51

Table 2.3 ANOVA results for tensile strength of composite structures ............................ 53

Table 2.4 Maximum deflection and maximum force during flexural testing of structures55

Table 2.5 ANOVA for flexural strength of composite structures ...................................... 57

Table 3.1 Specifications of 3D woven fabrics/reinforcements specifications ................... 67

Table 3.2 Physical and chemical properties of the green epoxy resin ............................... 69

Table 3.3 Tensile properties of 3D woven composites ...................................................... 73

Table 3.4 ANOVA for tensile strength of composite structures ........................................ 74

Table 3.5 Flexural modulus of 3D woven composites ...................................................... 76

Table 3.6 ANOVA for flexural strength of composite structures ...................................... 77

Table 3.7 Interlaminar shear strength of 3D woven composites ....................................... 79

Table 3.8 ANOVA for interlaminar shear strength of composite structures ..................... 80

Table 3.9 ANOVA for Charpy impact strength of composite structures .......................... 81

Table 3.10 CAI modulus of 3D woven composites ........................................................... 90

Table 4.1 Specifications of 3D woven spacer fabrics ........................................................ 98

Table 4.2 Physical and chemical properties of the green epoxy resin ............................... 98

Table 4.3 Physical testing results of the 3D woven spacer fabric .................................. 100

Table 4.4 Flexural modulus of 3D woven spacer fabric composites ............................... 104

Table 4.5 ANOVA for flat compression strength of composite structures ...................... 106

Table 4.6 Flat compressive testing results of 3D woven spacer fabric composites ......... 106

Table 4.7 Compression and recovery test results of 3D woven spacer fabric composites

.......................................................................................................................................... 111

Table 5.1 Combined comparative results of 3D composites (Stage 1) ............................ 119

Table 5.2 Combined comparative results of 3D composites (Stage 2) ............................ 120

Table 5.3 Combined comparative results of 3D spacer composites (Stage 3)................. 121

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LIST OF EQUATIONS

Equation 1.1 ....................................................................................................................... 24

1

RESEARCH OUTLINE

Three dimensional (3D) woven fibre reinforced polymer composites (FRPC) are currently

receiving a great deal of attention in numerous applications such as interior parts of

vehicles, light weight furniture, automotive, sporting goods, aerospace, civil infrastructure,

etc., due to their favourable mechanical properties. Despite their several advantages over

traditionally used structures, they tend to be susceptible to the different static and dynamic

mechanical loads (in plane and out of plane), resulting in the failure of the structure. A

substantial amount of experimental and theoretical work has been performed to understand

the in-plane properties as well as out of the plane performance of 3D woven composites

exposed to different mechanical loads. However, the use and influence of individual 3D

warp and weft interlocks and their combination with novel hybrid 3D interlocking on the

in-plane, as well as the out of plane properties of different 3D woven composites and, time

dependent performance of the 3D woven spacer composites has not yet been explored. The

behaviour of 3D woven (Solid and Spacer) composites under static and time dependent

loads are studied in this work.

Chapter 1

In this chapter, the literature survey is presented, and this is divided into five sections. The

first section deals with the general background of this study with a certain application area

and their significance. The second section deals with different classes of textile

preforms/reinforcements (2D and 3D), Advantages of three dimensional (3D) woven

structures over the two dimensional (2D) woven structures. Designing of 3D woven

structures on the conventional weaving machines. In the third section, types of the matrix

with their significance and composite fabrication techniques are explained. In the fourth

section, literature regarding the 3D woven composite with different reinforcement systems

is described in detailed. This also covers damage/failure mechanisms under tensile,

flexural, compression, compression after impact, impact testing, and the effect of test

parameters on the subsequent damage mechanism. In the fifth section of this chapter, the

research problem is defined, and the objectives of this study are stated.

Chapter 2

In this chapter, designing and fabrication of warp, weft and bidirectional (combination of

warp and weft) interlock 3D woven structures using the orthogonal layer to layer (OLL)

3D multilayer technique on a conventional weaving loom, is described. Influence of the

interlocking patterns on the mechanical properties (in plane and out of plane) of the

composite structures is explained in both warp and weft directions.

2

Chapter 3

In this chapter, designing and fabrication of 3D woven warp interlock structures using the

orthogonal layer to layer (OLL), orthogonal through thickness (OTT), angle layer to layer

(ALL), angle through thickness (ATT) interlocking and their combination (hybrid

interlock) with extra stuffer yarns in warp direction, is discussed. Also, the Influence of the

interlocking patterns on the mechanical properties (in plane and out of plane) of the

composite structures is clarified in both warp and weft directions. Microscopic images are

added for clarification of the 3D structures.

Chapter 4

In this chapter, designing and fabrication of the 3D woven spacer composites with different

thickness levels (4mm, 10mm, 20mm) and their influence on the mechanical (flexural,

impact, compression) as well as on the time dependent compression/recovery properties, is

explained. Effect of pile height on different mechanical properties is explained. The cyclic

load is applied to the composite structures to determine dynamic compression and recovery

behaviour.

Chapter 5

In this chapter, general conclusions and future perspectives of this work are given.

3

GENERAL ABSTRACT

Three-dimensional (3D) fibre reinforced polymer composites (FRPC) are attractive and

preferred in high performance applications because of their resistance against delamination

and better out of plane properties due to the presence of fibres/yarns in the z direction.

However, the ability to withstand damage depends on weave design, z-binder yarn and

interlocking pattern. A substantial amount of research has been performed to understand in

plane properties of 3D woven composites as well as under different mechanical loads. But

there is limited research on the damage tolerance and out of plane properties of 3D woven

warp, weft, bidirectional and novel hybrid interlock composites as well as on mechanical

and time dependent compression and recovery properties of 3D woven spacer composites.

In view of present research in 3D woven composites, two different types of 3D woven

reinforcements i.e. 3D woven solid and 3D woven spacer were developed. In 3D woven

solid reinforcements i.e. warp, weft, bidirectional and hybrid interlock structures were

produced. In the first stage, 3D orthogonal layer to layer warp, weft and bidirectional

interlock composite structures were fabricated. It was found that alone warp and weft

interlock composites showed better tensile behaviour as compared to bidirectional interlock

composite in warp and weft direction, due to the presence of less crimp as compared to

bidirectional interlock. However, bidirectional interlock composite exhibited considerably

superior impact resistance and three-point bending strength as compared to the individual

warp and weft interlock composites. In the second stage, mechanical performance of seven

different types of 3D woven composites i.e. orthogonal layer to layer (OLL), orthogonal

through thickness (OTT), angle interlock layer to layer (ALL), angle interlock through

thickness (ATT), hybrid 1 (H1, combination of OTT and ATT), hybrid 2 (H2, combination

of OTT and ALL) and bidirectional interlock (H3) were studied. Overall, during in plane

testing (tensile), OTT composite samples behaved mechanically well due to the least crimp

in binder yarn, while during out of plane characterizations (flexural, interlaminar shear

strength, low velocity impact and compression after impact), both through thickness

structures (OTT and ATT) and H3 samples showed highest and comparable mechanical

results. In the third stage, 3D woven spacer composites with three different thicknesses i.e.

4mm, 10mm and 20mm were characterized. Flexural, low velocity impact and flat

compression performance of the 3D woven spacer composites were reduced with the

increase of sample thickness. The highest amount of energy was absorbed during fracture

of 4mm thick composite. Compressibility (%) and resiliency (%) was highest in 4mm thick

composite but recovery (%) was found a bit lower as compared to the 10mm and 20mm

thick composites. While in 10mm thick composite recovery percentage was highest.

4

1 Chapter 1: Context of study

1.1 Background

Textile reinforced composites have been used successfully for decades in many sectors

such as automotive, furniture, aeronautics, sporting goods, marine, ground transportation

and off-shore industries. The existence of composite materials in these areas is due to their

high level of stiffness and strength that can be optimized for different loading conditions as

well as their low density, higher energy absorption (specific) and exceptional fatigue

behaviour [1], [2].

In recent years, a rapid growth in advanced composites has been seen in civil aircraft

programs such as the Boeing 787, Airbus A350XWB and the Bombardier C series. A

substantial volume of composites is now used in wind turbine blades and the automotive

industry. Traditional methods of composite fabrication based on hand lay-up, prepreg and

autoclave curing are expensive and a big impediment to high volume production [3], [4].

Whereas automated tape laying and fibre arrangement/placement procedures are

addressing throughput issues, the composite industry is seriously looking for dry fibre

preforms in combination with resin infusion procedures. Three dimensional (3D) woven

reinforcements/preforms are mainly attractive because of their reduced part count and low

manufacturing cost, as well as their capability to form near-net shapes as well as the

presence of through thickness yarns/reinforcements [5], [6].

Additionally, to the manufacturing costs and production rate, damage tolerance has become

an important issue for the composite industry. Resin toughening and through thickness

reinforcement are the general approaches used to improve damage tolerance; but the use of

through-thickness reinforcement is considered to be the most effective method [7], [8]. The

through-thickness fibres can be introduced using different types of textile processes,

including the 3D weaving, stitching, knitting and braiding or using specialist methods such

as pinning and z-anchoring. Weaving and braiding are the most promising technologies for

manufacturing three-dimensional (3D) textile structural composites [9], while 3D weaving

is the textile process that is capable of producing the highest volume production at the

fastest rate. 3D woven composites showed better through thickness properties in

comparison with the 2D laminate, such as improved impact damage tolerance, higher

interlaminar fracture toughness and reduced notch sensitivity [10]–[12]. The development

of new effective methods to produce more complex and thick 3D woven preforms for

composites has raised high expectations in the automobiles, ballistic protection,

construction and aerospace industries [13].

5

1.2 Woven structures/reinforcements

Woven structures are generally formed by interlacement of two sets of yarns [14].

Mechanical and physical properties of woven fabric structures mainly depend upon the

basic properties of fibres and yarns, fabric construction and weave design being used for

the manufacturing of fabrics. Woven fabric structures/reinforcements are categorized based

on weave patterns, dimensions, axis, weaving techniques and final product. Weave patterns

describe a way of interlacement of warp and weft yarns in the fabric structure. By

considering the constituent yarn woven structures can be categorized as two dimensional

(2D) and three dimensional (3D) woven structures/reinforcements [15].

1.2.1 Two dimensional (2D) woven structures

Two dimensional woven structures (reinforcements) are defined as the fabric structures

having two dimensions i.e. X (longitudinal) and Y (cross). Two dimensional structures are

achieved by interlacement of two sets of yarns (which are perpendicular to each other) in a

regular pattern or weaving approach as shown in Figure 1.1. The strength of structure is

sustained by the mechanical interlocking of the yarns.

Figure 1.1 Two dimensional (2D) woven structures

Laminated or 2D woven fabric reinforced polymer structure has been used with outstanding

success for over 65 years in maritime craft [16], for about forty years in aircraft industry

[17], [18] and for approximately thirty years in automobiles [19] and civil structures such

as in buildings and bridges [20]. Despite the usage of 2D laminated structures over a lengthy

period, their use in many structural and high-performance applications has been limited due

to the manufacturing problems and by some inferior mechanical properties. The application

of 2D structures/laminates in some critical application areas such as in some parts of aircraft

[16] and automobiles [19] has also been restricted by their lower impact damage resistance

and poor through thickness mechanical properties. The low through thickness properties,

such as flexural stiffness and strength, impact resistance and fatigue resistance, have

reduced the usage of 2D laminated structures in thick assemblies subjected to the through

thickness as well as in interlaminar shear stresses. The said problems in 2D laminates added

6

that many 2D laminates showed lower resistance to delamination cracking under low and

high-speed impact loading due to their inferior interlaminar fracture toughness.

1.2.2 Three dimensional (3D) woven structures

Three dimensional woven structures (reinforcements) are defined as the fabric structures

having a substantial thickness which is achieved by interlacing multilayer warp or weft

yarns with single weft insertion [21]. 3D woven structures [22]–[26] are also called

multilayer interlock structures [27]–[31]. Woven structures consisting of two or more

single layers, joined together at certain points whose distance from each other in warp and

weft directions is significantly larger than the basic weave repeat, is called multilayer

interlock structure. 3D multilayer woven structures are shown in Figure 1.2. Multilayer

interlock structures have three dimensions i.e. X (longitudinal), Y (cross), and Z (vertical).

The 3D woven structure is a single fabric structure wherein the component yarns are

theoretically inclined in the three mutually perpendicular directions [32].

Figure 1.2 Three dimensional (3D) or multilayer woven structure

A 3D woven preform also called 3D woven interlock is conventionally formed of warp (0º

direction) and weft (90º direction) stuffers that are bound together by a series of warp

binders. By varying the binding pattern, different 3D woven structures are produced. The

performance of woven preforms depends on the orientation of the binding patterns [33].

The structures in which the numbers of threads from different fabric layers are used to bind

the layers with each other are called as multilayer fabrics. A multilayer structure consists

of two or more layers, linked to one another at fastening points. The numbering of layers

is done consecutively from top to bottom.

Three-dimensional woven can be differentiated by pile/spacer yarn or multilayer

interlocking yarns as nominated as multilayer structures. So, 3D woven structures can be

classified into two major categories;

• Solid 3D woven structures (Multilayer interlocks)

• 3D Woven Spacer structures

7

1.3 Solid 3D woven structures

Solid 3D woven interlock reinforcements may be multilayer warp interlock or multilayer

weft interlock. In multilayer warp interlock structures, layers are joined together by warp

yarns whereas, in multilayer weft interlock structures layers are joined together with weft

yarns. While solid 3D multilayer interlock structures are further classified as [34], [35];

• Orthogonal interlock structures

• Angle interlock structures

• Hybrid interlock structures

1.3.1 Orthogonal interlock structures

Orthogonal multilayer interlock reinforcements are produced in a way that, warp yarns of

a layer are used to bind the other layers. Since warp yarns are used to connect the layers,

so no dedicated binding yarns are used. In orthogonal interlocks, z-direction yarns are

drawn through the warp and weft yarns, intersecting the layers at a 90 º angle. The yarns

are interlaced homogenously in each of the three planes to provide quasi-isotropic

properties or an unbalanced amount in each direction when anisotropic properties are

required [36]. In orthogonal through thickness (TT) interlock structure, some warp yarns

from the first and last layers are engaged to bind/hold all the layers present in the fabric as

shown in Figure 1.3. In an orthogonal layer to layer (LL) interlock structure, certain warp

yarns are used to bind two connective layers together and so on, as shown in Figure 1.4.

Figure 1.3 Multilayer orthogonal through thickness interlock structure

Figure 1.4 Multilayer orthogonal layer to layer interlock structure

8

1.3.2 Angle interlock structures

Multilayer angle interlock reinforcements/structures are produced in a way that binding

yarns passed from the fabric layers at a certain angle to bind all the layers. Angle interlock

structures mainly are also of two types, through the thickness (TT) and layer-to-layer (LL)

angle interlock structures. Through thickness angle interlock is a multilayer interlock in

which warp yarn travels from one face of the structure to the other, binding mutually all

the layers of the preforms as shown in Figure 1.5, while layer to layer angle interlock is a

multilayer preform in which warp yarn travels from one layer to the next layer, and back

as shown in Figure 1.6.

Figure 1.5 Multilayer angle interlock through thickness structure

Figure 1.6 Multilayer angle interlock layer to the layer structure

The orthogonally woven 3D reinforcements usually have a smaller geometrical repeating

unit cell than angle interlock reinforcements [36]. The performance of 3D woven structures

is determined by the binding pattern. Under the same conditions, an angle interlock

possesses better pliability and forming capability, whereas orthogonal interlock binding

provides a greater fibre volume fractions, especially in through thickness direction [37].

In 3D woven structures, through thickness yarn is responsible for strength, stiffness and

thickness of the structure in the thickness direction. These structures showed improved

mechanical properties as compared to 2D structures due to its structural stability in the

transversal direction [38]. In the aerospace and automotive industries, a composite based

on 3D woven preforms are preferred for their better structural properties [39]. These

9

integrally-woven 3D structures give composites that are less notch-sensitive and exhibit

high strain, in both compression and tension.

1.3.3 Hybrid interlock structures

In general, 3D woven structures (reinforcements) are made up of only one type of

interlocking pattern. But in hybrid interlock structures, a combination of two, three or four

basic types of 3D multilayer interlocking patterns i.e. orthogonal layer to layer, orthogonal

through thickness, layer to layer angle interlock and through thickness angle interlock, can

be used. Similarly, hybridization can also be done by combining warp and weft interlocks

in one structure keeping in view the required properties. Furthermore, hybridization can

also be made in terms of material by selecting different material types in warp and weft

directions of the structure [40]. The specific sequence of yarn placement can also be

achieved in both directions. 3D multilayer hybrid structure can be produced by combining

both; different types of interlocking patterns and yarn materials keeping in view the cost

and target properties [9], [41]–[43]. Since interlocking and straight warp (stuffer) yarns

help to improve the in plane as well as out of plane mechanical properties of the 3D woven

structures. Therefore, these (interlocking and stuffer) yarns could be added in different

places of the woven structures to improve their properties. These 3D hybrid woven

structures with different types of interlocking patterns can also be produced on

conventional dobby/jacquard looms as shown in Figure 1.7.

Figure 1.7 Multilayer hybrid woven structure

1.4 3D woven spacer structures

3D woven spacer structures (reinforcements) are the fabrics in which two outer layers of

the structure are joined together by means of vertical yarns/loops also called as pile yarn

[44], [45], as shown in Figure 1.8. Spacer fabrics consist of three sets of yarn including

warp yarn, weft yarn, and spacer/pile yarn. Spacer fabrics have better compression

behaviour, impact resistance, thermal insulation, thermal conductivity and air permeability.

10

Figure 1.8 3D woven spacer structure

Due to better air permeability spacer fabrics are widely used in sports clothing and because

of good absorbency they are used in medical textile. Spacer fabrics are also used in

technical textiles such as in geotextile as reinforcement material between aggregate or soil

stone and in roads, railways work, erosion prevention and separation.

Weave designs of 3D woven solid and spacer structures/reinforcements are discussed in

this section.

1.5 Weave design of solid 3D woven multilayer interlock structures

1.5.1 Weave design of orthogonal layer to layer interlock

An example of two-layer interlock structure is shown in Figure 1.9. This showed the

weaving of a two-layer interlock structure, the individual weave of each layer is plain. It is

the simplest example of a multilayer structure [46].

Figure 1.9 Cross sectional view of two layers structure

First (top) layer is called the face (F) and second (bottom) is called the Back (B) layer. On

graph paper, their plain weave design is marked with different signs, as shown under:

X O

X O

Face weave (F) Back weave (B)

In the resultant design of the multilayer fabrics, the ends are arranged in Face-Back-Face-

Back order and picks are also arranged in the same Face-Back-Face-Back sequence,

11

resulting into a two-layer tubular structure. The repeat of this design is completed on 4 ends

and 4 picks.

Repeat size

Weave design repeat = R = LCM of weave designs × number of weave designs.

We have two weave designs, that is, 1/1 and 1/1.

Therefore, for LCM (least common multiple)

We have two weave designs = 1 + 1, 1 + 1

= 2, 2

So, LCM of two weave designs = 2

And the number of weave designs = 2.

Finally,

Repeat size = R = LCM of weave designs × number of weave designs.

Repeat size = R = 2 × 2.

Repeat size = R = 4.

The complete weave design will be on 4 ends and 4 picks, Rules of interlacement for

multilayer weave are given as under:

Rule-1: Face ends will only interlace with face picks.

Rule-2: Back ends will only weave with back picks.

Rule-3: All the face ends should be raised on all the back picks.

This stitching/interlocking forms the foundation of 3D weaving. We can stitch/interlock

number of layers together forming a very thick 3D woven fabric. There are three different

techniques used for stitching different layers together raiser stitching, sinker stitching and

extra end stitching. In this work, raiser stitching technique is used. Raiser stitching means

certain back layer ends are raised over certain face picks [47] as shown below in Figure

1.10.

Figure 1.10 Cross sectional view of raiser stitching/interlocking of two layers

The resultant weave design of orthogonal layer-to-layer structures having raiser

stitching/interlocking would be; Sinker stitching means certain face layer ends are lowered

under certain back picks as shown below in Figure 1.11.

12

S = back ends raised from the front picks

X = Ends are passing over the pics Figure 1.11 Weave design of two-layer orthogonal layer to layer interlock with raiser

stitching/interlocking

1.5.2 Weave design of orthogonal through thickness interlock

In orthogonal through thickness structure, some warp yarns from the first and last layers

are used to bind all the layers present in the fabric. The formula to calculate the repeat size

of orthogonal through thickness stitched structures is the same as of orthogonal layer to

layer stitched structures but, having two extra ends for through thickness stitching. All the

multilayer rules are similar to layer to layer orthogonal structure [46].

The weave design of 6 layers orthogonal though thickness stitched structure having plain

weave in every layer is given in Figure 1.12; (Repeat size = 14 ends x 12 picks)

X = Warp ends are passing over the running picks

Figure 1.12 Weave design of six layers orthogonal though thickness structure

1.5.3 Weave design of layer to layer angle interlock

In orthogonal structures, weave design could be drawn just by knowing the number of

layers in the structure. But in angle interlock structures first, we must draw the cross section

of the design and repeat size should be marked from the cross section. Then in cross section,

the numbering of the layers in warp and weft direction is done [46].

13

For example, we want to make a six-layered layer to layer interlock angle interlock

structure. First, we draw the cross section of the fabric design and numbering of layers is

done both in warp and weft direction as shown in Figure 1.13.

Figure 1.13 Cross section of six layers layer to layer angle interlock structure

Keeping in view the cross section of the design, weave design of six layered layer to layer

stitched angle interlock structure could be drawn on graph paper which is given in Figure

1.14.

X = warp ends are passing over the running picks

Figure 1.14 Weave design of six layers layer to layer angle interlock structure

14

1.5.4 Weave design of through thickness angle interlock

Like layer to layer angle interlock structure, first, we draw the cross section of design and

secondly numbering of the layers is made both in warp and weft direction for through

thickness angle interlock structure [46].

For example, we want to make a three layered through thickness stitched angle interlock

structure. First, we draw the cross section of the fabric design and numbering of layers is

done both in warp and weft direction as shown in Figure 1.15.

Figure 1.15 Cross section of the three layered through thickness angle interlock structure

Keeping in view the cross section of the design, weave design of three layered through

thickness stitched angle interlock structure could be drawn on graph paper which is given

in Figure 1.16.

X = warp ends are passing over the running picks

Figure 1.16 Weave design of three layer through thickness angle interlock structure

15

1.6 Weave design of 3D woven spacer structure

Weave design of spacer fabric consists of three sets of yarn including warp yarn, weft yarn

and spacer/pile yarn. Cross sectional view of a 3D spacer structure is shown in Figure 1.17.

A combination of loose reed (LR) and fast reed (FR) beating up mechanism is used to

produce 3D woven spacer structures on terry loom. The purpose of the loose reed is to

collect a certain number of picks unbeaten and then beaten through fast reed mechanism to

get compact picks on terry loom [46].

Figure 1.17 Cross sectional view of 3D woven spacer structure

Weave design of 3D spacer structure as per cross section is given in Figure 1.17 is given in

Figure 1.18.

16

LR=Lose Reed, B=Back layer, S1=S2=Pile yarn,

FR=Fast Reed, M= Middle layer, G1=G2=G3=G4=Ground yarn,

F=Face layer

Figure 1.18 Weave design of 3D woven spacer structure

For weaving of 3D woven spacer fabric structure loom having two beams loading capacity

(Terry loom) is selected. Two weaver beams are prepared due to the difference in yarn

crimp, one for the top and bottom ground weaves and another beam for pile yarns in the

central portion of the structure. Loose and fast reed options are used depending upon the

repeat of ground and pile yarns.

1.7 Polymer matrix

Polymer or resin as matrix material can be processed easily, lightweight and offer desirable

mechanical properties. The resin as the matrix has a very critical role in the composite

material. When fibres/reinforcements are glued with resin, fibres bear the external load and

resin distributes the external load to all fibres. In the load distribution mechanism, the most

important portion is the fibre matrix interface. Resin prevents fibre buckling underneath the

compressive load, giving them structural integrity. Apart from these, the resin has other

roles also:

• Protection of the surface from wear and tear, abrasion, corrosion etc.

• Minimize stress concentration

• Resist high temperatures

• Resist microcracking in the composite

Considering the nature of the polymer, these materials can be classified into two

categories:

• Thermoplastic resin

• Thermoset resin

In thermoset composites, especially epoxy resin is widely used in aeronautical, aerospace

and naval structural applications. Thermoset polymers curing process is irreversible

because cross-linking initiates due to the chemical reaction [48]. They decompose rather

than melting when heated after cure. Being chemically inert, temperature resistant and

having good mechanical properties, thermoset resins are most widely used. The curing or

cross-linking is initiated by a free radical initiator such as organic peroxide, converting low

viscosity resin to a three dimensional thermoset plastic [49]. Thermoplastics polymers are

changed to liquid when heated and frozen to glassy or solid state when cooled adequately.

They need to be moulded at an elevated temperature that is above their melting point which

is sometimes a big problem for large structures [50].

17

Thermoset resins

These are the polymers which degrade on heating without going through the fluid state

[48]. Thermosetting resins are preferred over the thermoplastics due to their low viscosity

and low temperature crosslinking/polymerization. They decompose rather than melting

when heated after cure. Being chemically inert, temperature resistant and having good

mechanical properties, thermoset resins are most widely used. The related problems are

toxicity and non-recyclability. They exist in two or more components which are mixed

together just before the curing process. Catalyst and inhibitor are also added to control the

chemical reaction. The degree of cure and gel point are two key parameters for the complete

study of thermoset resins.

The degree of cure (α)

The degree of cure is the quantification of cross-linking of molecules (extent of chemical

reaction) in thermoset polymer while curing. Sometimes it is also called the degree of

conversion of reaction.

Gel point (αgel)

A cross-linked polymer at its gel point is a transition state between a liquid and a solid. The

polymer reaches its gel point is a critical extent of cross-linking (αgel) at which polymer

stops flowing like a liquid. The mechanical properties of resin start to develop from this

point. It cannot be detected by differential scanning colourimetry (DSC),

thermogravimetric analysis (TGA). Generally, the gel point of a resin is determined

rheologically [51].

Glass transition temperature (Tg)

It can be defined as “The point at which the glass transition temperature ‘Tg’ of the

polymer has become equal to the cure temperature”. At this point, the polymer is

transformed to a glassy state from the rubbery gel state and vice versa.

Epoxy resin is used in this study and briefly discussed below:

1.7.1 Epoxy resin

Epoxy resins consist of oligomers having oxirane which cure through the polymerization

of an epoxide group with the suitable curing agent. Now a day, a wide range of epoxy

polymers of varying properties are available. For epoxies;

• A minimum of pressure is required for manufacturing of products used for

thermosetting polymers.

• Shrinkage during curing should be much lesser to avoid or reduce residual stresses.

• Usage of the wide range of temperatures by careful selection of curing agents which

allows the decent control over the degree of cross-linking during curing.

18

Due to these exceptional features and beneficial properties of polymer systems, epoxy

resins are commonly used in the structural applications, engineering composites, surface

coatings, and electrical laminates. Maximum of the composite applications use di-

functional epoxy as a matrix. However, epoxies with the higher functionality, known as

multifunctional (Tri- and tetra-functional) epoxies, are used in many high-performance

applications such as aerospace and critical defence applications. The choice of curing

agents (also called hardener) for epoxies depends on the applicable curing conditions and

final applications of the resin. Epoxies can be cured with amines, alcohols and thiols. Below

are given some examples of commercially used epoxies resins (Figure 1.19). In this work

Diglycidyl ether of bisphenol A (DGEBA) epoxy resin is used with aliphatic amine

hardener.

Figure 1.19 Chemical formulation of different epoxy resins [52]

Bisphenol A based epoxy resin is used in this work and chemical formulation of said epoxy

is shown in Figure 1.20. Epichlorohydrin (ECD) is allowed to react with Bisphenol A

(BPA) in presence of NaOH to get epoxy resin. If ECD is obtained from the natural

renewable resources then epoxy will be environmental friendly or green. Generally, ECD

19

is formed by the reaction of polypropylene with chlorine. But in green epoxy, ECD is

formed by reacting glycerine with HCl (Spolchemie). Degrading parentage of the resin

depends upon the percentage of green ECD in the epoxy resin.

Figure 1.20 Manufacturing cycle of the bisphenol A based epoxy resin [52]

“Amines are widely used as hardeners for epoxy resins. Amines used for curing epoxy

resins can be grouped into three categories: aliphatic, cycloaliphatic, and aromatic. The

reactivity of the amine increases with its nucleophilic character: aliphatic > cycloaliphatic

> aromatic. The advantage of aliphatic amines is that they can cure epoxy resins at ambient

temperature. Other amines mostly require heat curing. Heat curing is difficult and

impractical for the fabrication of certain structures and requires a significant amount of

energy. Ambient curing saves energy and is advantageous for coating or adhesive

applications. Although the curing takes place at room temperature, for completion of the

curing reaction it is necessary to post-cure at a high temperature”.

During the curing reaction, two epoxy rings react with a primary amine (Figure 1.21). The

first step is the reaction between the primary amine hydrogen with the epoxy group,

followed by a reaction between the secondary amine hydrogen with another epoxy.

20

Figure 1.21 Mechanism of curing of epoxy resin with amine hardener [52]

“Although a single activation energy and heat of reaction are experimentally obtained for

both steps, the reactivities of primary and secondary amino groups may be different. The

hydroxyl groups generated during the cure can also react with the epoxy ring, forming ether

bonds (etherification). The etherification reaction completes with the amine-epoxy cure

when the reactivity of the amine is low or when there is an excess of epoxy groups”. While

environmental friendly green epoxy resin is also used to protect the environment from

hazardous chemicals. Green epoxy resin will degrade and the whole structure will destroy

the afterlife. Different types of green epoxies are available with different grades. The

difference in the manufacturing cycle of green and conventional epoxy resin is shown in

Figure 1.22. Comparison of epoxy properties with other thermoset resins is given in Table

1.1.

Figure 1.22 Manufacturing cycle of normal and green epoxy resin

21

Table 1.1 Comparison of properties of different resins

Type of resin

Tensile

strength

(MPa)

Ultimate

tensile

strength

(MPa)

Flexural

modulus

(GPa)

Young's

modulus

(GPa)

Density

(kg/m3)

Strain

at

rupture

(%)

Tm

(˚C) Tg (˚C)

Cure

shrinkage

(%)

Vinyl ester 80 75-90 3.1 3.3 1120 5 - 60 5.4-10.3

Epoxy 85 35-140 10 10.5 1150 0.8 - 130, 180 1-5

Unsaturated polyester 65 70 4 4.3 1100 3.5 265 73 5-12

1.8 Fibre reinforced polymer composites (FRPC)

The composite material is the combination formed by the physical combination of two or

more components on a macroscopic scale to form a beneficial material often displaying

features that none of the individual component exhibit. Such heterogeneous materials fulfil

specific requirements of depending upon desired design and function. The primary

constituents of composites are reinforcement and matrix. Fibre reinforced polymer

composites (FRPC) are the most extensively used in different applications. Everyday

examples like water storage tanks from glass fibre polyester resin to high tech specialized

applications in Boeing 787. FRPC has excellent mechanical properties like specific strength

and specific stiffness [53]. FRPC is used in the diverse application ranging from golf club

rackets to missile systems.

In recent trends, composites are substituting metals and other heavy materials, due to

following characteristics [50]:

• High specific strength

• Choice of shape

• The material can be tailored

• Exceptional fatigue strength

• Resistance against chemicals, acids etc.

• Better weather/water resistance

• Excellent impact resistance

Based on resin types, composites classification is shown in Figure 1.23. In the present

study, thermoset resin is used.

22

Figure 1.23 Composite classification based on the matrix types

Reinforcement is the group of fibres. It carries the stress applied on composite and plays a

key role in the mechanical performance of the composite. The competency of the composite

can be checked by distribution, length, shape, orientation, the composition of the

reinforcement and mechanical performance of resin. Alignment of fibres in resin decides

the strength of the composite and it is highest along the longitudinal direction of the fibre.

Reinforcements can stand against a maximum load in its direction. But, any shift from the

fibre axis considerably decreases its load-bearing capacity. Composite materials have

excellent fatigue resistance, high strength to low density, high stiffness and high corrosion

resistance. Based on the physical state of reinforcement, composites are of following types:

• Fibre reinforced composites

• Particulate composites

• Structural composites

Fibre reinforced composites are appeared as a possible alternative choice to metal

components in engineering applications due to their high strength and/or stiffness ratios,

excellent mechanical properties, the potential for cost-effective and their easiness of

adaptability into complicated shapes. Woven, knitted, braided and stitched structures are

mostly used to prepare near net shape fibrous preforms for engineering applications.

Chopped fibres (nonwoven), filament yarn, fabric, and advance three-dimensional fabrics

are major types of reinforcements in FRPC. Three types of reinforcements are in use having

certain fibres for composites manufacturing which are;

1- Unidirectional (tows, yarns) (UD)

23

2- Bidirectional (woven fabric, felts, mats) (2D)

3- Three-dimensional (multidimensional fabrics) (3D)

Depending upon the type of reinforcement, composites are also divided into three major

categories i.e. UD, 2D and 3D composites. In the present study, three dimensional (3D)

woven solid and spacer reinforcements are produced using the multilayer interlock

techniques which are discussed in detail in the first section.

Some commonly used reinforcements include glass fibre, para-aramid fibres or carbon fibre

from the synthetic origin. Glass fibre is the major shareholder in FRPC. Because, it is the

cheapest, easily available and offer suitable properties for the composite fabrication.

Different natural fibres are also used in the reinforcements for composite fabrication.

Natural fibres are divided into animal, mineral and vegetable fibres. Mineral fibres are not

preferred in technical applications due to their carcinogenic properties. Vegetable fibres

like jute, flax, hemp and cotton are composed of cellulose, while animal fibres like wool,

silk and hair consist of proteins. Vegetable fibres are categorized as hair, leaf and bast

fibres, depending on their source. In plants, leaf and bast fibres provide mechanical strength

to the leaf or stem respectively. Natural fibre classification is shown in Figure 1.24 [42].

The topography of natural fibres is irregular and rough and provides good sticking to the

resin in a composite structure [54]. Choice of fibres depends on end use including:

• Breaking elongation

• Thermal instability

• Fibres and matrix adhesion

• Ultimate cost

Figure 1.24 Classification of natural fibres

24

In the present study, E glass filament yarn and carbon tow from synthetic origin while jute

spun yarn from natural origin were used in the reinforcements, properties of some

commonly used fibres are given Table 1.2 [55], [56].

Table 1.2 Properties of different fibers

Fiber type Tensile strength

(MPa)

Ultimate

tensile strength

(MPa)

Flexural modulus

(GPa)

Youngs modulus

(GPa)

Densit

y (kg/m

3)

Strain

at rupture

%

Price/kg US$

Compressive Strength

(MPa)

Compressive Modulus

(GPa)

Glass (E) 2400-

3500 3450 47.7 72 2550 1.8-3.2 1-2.5 450 1.3

Polyamide

(6 6) 82-90 79.28 2.826 3.3 1150 50-100 2.5-5 60 2.4

Polyethylene 15-40 2300 1.15-1.2 0.5-1.5 970 400 2.5-4 20 0.7

Jute 400-

800 400-800 3.4 10-30 1440 1.5-1.8 0.5 - 0.35

Steel 1250 520-720 - 210 7850 - 3-5 - -

Aluminium 140-

620 310 - 70 2700 10-12 1.5-3.5 3400 82

Kevlar 2300-

3400 2757 - 73-99 1440 1.9-4.0 25 350-450 -

Polyamide (6) 78 45-90 1.2-1.4 2.6-3.0 1084-

1230 50-100 2-4 55 2.3

Fibre volume fraction is the volume of fibres present in the composite. It is an indicator of

mechanical properties of the composite. Fibre volume fraction for any composite can be

calculated by the Equation 1.1 [54].

𝑉𝑓 =

𝑚𝑓

𝑑𝑓𝑚𝑓

𝑑𝑓+𝑚𝑟

𝑑𝑟

Equation 1.1

Vf represents the fibre volume fraction, mf denotes the mass of fibre, mr represents the mass

of resin while df and dr denote the density of fibre and resin respectively in the composite.

1.9 Thermosetting composite fabrication techniques

Different methods are used for thermosetting composite fabrication. The preference of

fabrication method for a specific composite part depends on the material, design of the part,

and the end use.

Thermosetting polymer matrix composites can be manufactured by the following

techniques:

25

Open moulding

Open moulding involves either hand layup or sprays up using the one side mould. In the

first step of hand layup, the mould is treated with gel coat (non-sticking agent). In the

second step, fibre layers are stacked/laid upon the tool. Consolidation is achieved by using

a pressing roller to remove air bubbles. While, in the spray-up method, chopped fibres with

catalysed resin are sprayed onto the mould.

Compression moulding

In this technique, a mould and a counter-mould are used for fabrication of composite parts.

The counter mould closes the mould after the embedded preform is positioned on it. The

compaction/consolidation is also achieved by the same counter-mould.

Resin transfer moulding (RTM)

In RTM, the resin is infused into a fibrous preform. For fabrication, the dry reinforcement

is positioned into the mould and the mould is closed. The resin is supplied into the mould

at low to moderate pressure through the injecting ports. This technique appears to be best

matched for medium volume, small to medium-sized complex parts.

Vacuum-assisted resin transfer moulding (VARTM)

This technique uses an open mould, on the top of which the reinforcements are placed. A

sheet of soft plastic is used to seal the boundary of the mould. Vacuum pressure is applied

under the piece of plastic. Resin enters the structure through the injecting ports and drawn

by vacuum through reinforcement. The air bubbles are removed and the composite piece is

compacted.

Filament winding

Filament winding method is used for a continuous fabrication of cylindrical geometries. A

long cylinder-shaped part called as the mandrel is horizontally positioned. The reinforcing

fibres pass through the resin bath and wound on to the mandrel. The dried part is ready for

use.

Pultrusion

Pultrusion is a relatively simple, low-cost and continuous process. Fibrous reinforcements

are allowed to pass through the resin bath, specific mould shape and then cured. After

cooling, the resultant shape is cut into specific length [57].

Open mould technique in combination with compression moulding is used in this work for

fabrication of different 3D woven composites.

1.10 Application areas of fibre reinforced composites

Textile fibre reinforced composites have been used successfully for decades in many

sectors such as automotive, aeronautics, sporting goods, marine, ground transportation and

26

off-shore industries. The existence of composite in such areas is because of their high levels

of stiffness and strength that can be optimized for specific loading conditions as well as

their low density, higher energy absorption (specific) and better fatigue performance [1],

[2]. Interior parts of automobiles and lightweight composite furniture are major

applications.

A significant volume of production is now used in wind turbine blades and the automotive

industry. The materials to be used in the automotive industry required to be lightweight,

cheaper, crashworthiness and recycle-able for environmental protection. Over 75% of fuel

consumption directly relates to automobile weight, and a 20% weight reduction could yield

12–14% fuel economy improvement [58]. It has been assessed that for every 10% of weight

reduced, fuel consumption reduced to 7%. Also, if 1 kilogram of vehicle weight is reduced,

then about 20 kilograms less carbon dioxide is produced [59], [60]. European Union in

2006 implemented a legislation that a substantial percentage of vehicles should be re-used

or recycled. In the United Kingdom (UK), every year About two million vehicles reach the

end of their life. It also sets higher targets to reuse and recycling of vehicle parts

(Environment agency, 2010) [59], [60].

3D woven preforms are particularly attractive because of their reduced part count and low

manufacturing cost, as well as their ability to make near-net shapes as well as the presence

of through thickness fibres or yarns [4]–[6], [61]

Resin toughening and through thickness reinforcement are the general approaches used to

improve damage tolerance; but the use of through-thickness reinforcement is considered to

be the most effective method [7]–[9]. 3D weaving is the textile process capable of

producing the highest volume production at the fastest rate and their corresponding

composites have better mechanical properties in the transversal direction [10], [12], [62],

[63]. The development of new effective methods to produce more complex and thick woven

preforms for composites has raised high expectations in the military and aerospace

industries [13]. It was 1972 when weaving was first used to produce 3D woven carbon-

carbon composites for brake components of jet aircraft [64]. However, research and

development of 3D woven composites remained low until 1980. But nowadays, interest is

developed in the development of 3D woven fabric for composites, as cost-effective and

damage resistant components became necessary in the automobile and aerospace industry

[65].

1.10.1 Composite characterization methods

Depending upon the application area composite structures undergo different types of static

and dynamic mechanical loads i.e. tensile, impact, flexural, compression, compression and

27

recovery, puncture resistance (needle penetration), short beam shear (SBS), Dynamic

mechanical analysis (DMA), Details of the different test are given below:

Tensile test

“A tensile test, also known as tension test, is probably the most fundamental type of

mechanical test you can perform on composite material. By pulling, quickly determine how

the material will react to forces being applied in tension. As the material is being pulled,

you will find its strength along with how much it will elongate”. Universal tensile strength

tester, with the standard test method ASTM D3039, is used for this test used to test the

tensile properties.

Impact test

“Impact test measures the ability to resist high rate loadings. An impact test is a test for

determining the energy absorbed in fracturing the specimen”. Impact testing is of two types

i.e. Pendulum and drop weight impact test. Pendulum impact test is further classified into

two sub-categories i.e. Charpy impact test and Izod impact test. The charpy impact test is

used for the impact strength of composite samples following the standard test method ISO

179 while for Izod impact testing ISO 180 test method is used. The drop weight impact test

is performed using ASTM D 7136 standard test method on drop weight impact tester. Drop

weight impact did not cause the complete destruction of the specimen and residual energy

can be determined.

Flexural test

“The flexural test method measures the behaviour of composite materials subjected to

simple beam loading. It is also called a transverse beam test. The purpose of a flexural test

is to measure the flexural strength and flexural modulus. Flexural strength is defined as the

maximum stress at the outermost fibre on either the compression or tension side of the

specimen”. The flexural test is of two types i.e. three-point and four-point flexural tests.

Three-point bending test (for flexural strength) is performed on the universal tensile testing

machine as per ASTM D7264 while Four-point bending test is performed using ASTM

D6272 standard test method.

Compression test

“Compression testing is a very common testing method that is used to establish the

compressive force or crush resistance of a material and the ability of the material to recover

after a specified compressive force is applied and even held over a defined period”.

Compression test of two types i.e. flat compression and edgewise compression. Flat

compression is performed using ASTM C365 standard test method while edgewise

compression is performed using ASTM C364 test method. Single compression and

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recovery test (ASTM F36) and cyclic compression and recovery test also performed using

the universal testing machine.

Puncture resistance test

“Puncture resistance is a measure of the maximum force or energy required to penetrate a

material. Puncture resistance depends on the nature of puncture attempt, with the two

most important features being point sharpness and force”. For needle penetration or slow

penetration resistance test EN 388, the standard test method is performed using the tensile

testing machine.

Short beam shear

“As the name implies, the short beam shear test (SBS) subjects a beam to bending, just as

flexural testing methods do, but the beam is very short relative to its thickness”. Short beam

shear test is performed using ASTM D2344 standard test method.

Dynamic mechanical analysis test

“The dynamic mechanical analysis is a high precision method for determining the

viscoelastic behaviour of materials. Most of the real-world materials display mechanical

responses that are a mixture of viscous and elastic behaviour”. Dynamic mechanical

analysis technique divides the dynamic modulus of materials into two distinct parts: an

elastic (storage modulus) component and viscous (loss modulus) component. Storage

modulus is the component of the dynamic modulus, where the strain is in phase with the

applied stress, and loss modulus is the component of the dynamic modulus, and where the

strain is 90° out of phase with the applied stress. The ratio of loss to storage modulus gives

the tangent of the phase angle delta, and tan delta is known as the damping which is a

measure of energy dissipation. Generally, dual cantilever test is performed using the

standard test method ASTM D7028.

1.11 Importance of fibre reinforced polymeric 3D woven composites

Fibre reinforced polymer composites are used in the automobile and aerospace industry

because of their high specific strength and stiffness, superior corrosion resistance and

improved fatigue properties. Different types of reinforcing geometries like unidirectional,

bidirectional (woven, knitted), three-dimensional (woven, knitted), nonwoven sheets,

chopped fibres are used in structural composite applications. Impact behaviour of

bidirectional laminates is better than chopped strand mats and nonwoven reinforced

laminates due to the presence of interlacements [66]–[68]. Among all textile reinforced

composites, woven structures have the large toughness to the initiation of interlaminar

crack [69] and plain weave design [70] (has maximum crossover points) acts as stress

distributor during impact testing [71], [72]. The presence of third-dimensional fibres in 3D

29

textile preforms (angle interlock and orthogonal woven, multi-axial warp knitted,

multilayer interlock and stitched) not only obstructs the delamination and crack propagation

but also increases the impact resistance and damage tolerance of the composites [72]–[76].

Different researchers used pinning and stitching techniques to improve the damage

resistance and damage tolerance [77]–[79] by using different types of high performance

fibres like Kevlar and glass for stitching, resulting in the change in material in-plane

mechanical properties. The tensile strength of the stitched laminates was slightly improved,

unchanged or 30~45% reduced, while compressive strength loss was 5~55% in magnitude

[78].

More specifically, 2D fabrics and unidirectional carbon and glass fibre reinforced plastics

are attractive materials for primary structures in higher performance applications.

Performance in a structural application may be optimized by tailoring the orientation of the

resin pre-impregnated fibre sheet (prepreg) prior to fabrication [80], [81]. However, the use

of these unidirectional prepreg sheets can be compromised under different loading

conditions such as impact, machining or lightning, due to low interlaminar performance.

Various concepts have been proposed to improve the interlaminar strength or damage

tolerance properties of structural composites. These include Interleafing, matrix

toughening, high strain fibres, yarn hybridization, reinforcement hybridization and the use

of 3D reinforcements [8], [82].

Three dimensional (3D) structures are introduced in structural composites capable of

withstanding multidirectional stresses. 3D Weaving is one of the most promising

technologies for manufacturing 3D near net-shape preforms. With this technique, the

desired mechanical properties can be achieved by arranging the fibres along the length,

width and thickness of the fabric. The significant improvement in interlaminar shear

strength is the greatest advantage gained by the arrangement of through-thickness yarn [11],

[64].

1.12 Impact testing and failure modes of 3D woven solid composite structures

Although the impact phenomenon can be categorized into either low or high velocity based

on the impactor velocity, a clear opinion about it does not exist. Impact at the speed range

of 1-10 m/s is considered as low velocity impact while impact in the speed range > 100 m/s

and >1000 m/s are termed as high and hyper-velocity testing. Cantwell and Morton [83]

classify low velocity impact as <10 m/s by considering different impact techniques,

whereas Abrate [81] states that low velocity impacts occur at a speed of less than 100 m/s.

Alternatively, Joshi and Sun [84] and Liu [85] characterized impact testing based on the

30

damage that occurred during impact loading. High velocity is defined as fibre breakage

through penetration and low velocity by matrix cracking and delamination.

A low velocity, high mass drop weight tester simulates the impact created by dropped tools

on a structure, whereas impact by an air gun system with a high-velocity small mass

projectile replicates flying debris during the take-off and landing of aeroplanes [81], [83],

[86]. Low velocity impact can be replicated by using the Charpy, Izod, and drop weight

impact fixtures. The Charpy and Izod are classified as destructive test methods, and provide

some failure modes that were not observed on operational structures under low impact

loading; whereas drop weight impact does not cause the complete destruction of the test

specimen and the residual energy can be determined when required [83]. Furthermore,

Palazotto et al. depicted the damage initiation in Z fibre reinforced panels. Pendulum

impact tester was used to check the threshold of energy levels at which significant damage

starts. Ultrasonic inspection, microscopic inspection and acoustic emission tests performed

to analyse the damage [87].

Figure 1.25 [88] showed the energy absorption of 2D and 3D woven composites under

impact. In Ko. and David’s [89] study of the impact behaviour of E-glass/epoxy composites

reinforced by 3D orthogonally woven and 2D biaxial woven fabric. it could be concluded

that the impact resistance of composites is characterizable in terms of damage area and

damage initiation as well as propagation energy. With the visual observations of specimens,

these parameters can be used to assess the impact behaviour of composites. It was observed

that 3D woven composites have less damage area than 2D woven composites, while the

damage initiation point was also close to the composites maximum load as shown in Figure

1.26.

Figure 1.25 Impact energy absorption of textile composite [88]

31

Figure 1.26 Impact response of 3D and 2D woven composites (a) 3D orthogonally woven

(b) 2D Plain woven (arrows represent the incipient damage points in 3D and 2D woven

composites) [89]

The drop weight impact test is a common method to investigate the impact resistance of

composite materials in which drops masses with different energies are dropped on the same

set of specimens supported on a horizontal plane. The impact event does not cause complete

destruction of the test specimen and allows one to evaluate progressive degradation and

damage tolerance with increasing impact energies. Impact energy can be varied, either by

changing the mass or changing the height of the drop. Different variables such as impact

force, impact energy, deflection, rebound velocity and the acceleration of the projectile are

recorded during the test. In fibre reinforced composites, impact damage is a combination

of four major failure modes:

1) Matrix cracking - where cracking occurs parallel to the fibres due to tension,

compression and shear stress concentration.

2) Delamination - produced by stiffness mismatch at the interface.

3) Fibre breakage - in tension, fibre breakage and in compression, fibre buckling.

4) Perforation - where the impactor is perforated through the impacted plate [90]

Impact damage and the subsequent tolerance of a composite structure is influenced by test

conditions (striker mass and velocity and structural support) and composite properties

(thickness, fibre/matrix interface, stiffness and the lay-up sequence). All these parameters

determine the mode and geometry of the damage zone [81].

During the fracture of 3D woven composites, the through thickness reinforcement not only

restricts the delamination by increasing interlaminar fracture toughness but is also

responsible for crack arresting and deviating [63], [91]. Brandt and Drechsler [62] observed

that under comparable test conditions, the through-thickness yarn (z fibres) in a 3D woven

structure suppresses delamination and absorbs higher impact energy than 2D woven

( a ) ( b )

32

laminates. This reduced sensitivity to delamination also leads to an improvement in residual

compression strength after impact. The fracture behaviour of 3D composites also

demonstrates that through-thickness fibres hinder the propagation of delamination although

the fibre damage during the manufacturing process may reduce the strength and fracture

resistance of a component [92].

In 3D reinforcements, the fibres/yarns are oriented in various in plane and out of plane

directions. The presence of through-thickness reinforcement provides strength and

delamination resistance, as well as better resistance to crack as compared to 2D laminates

[64]. Damage tolerance of fibre reinforced composites becomes an issue, as they may suffer

damage during their manufacturing, assembly, maintenance or service life, caused by

accidental blows, occasional overload and misuse. Such damage may not be detected in a

routine visual inspection of the component [93].

Metals can easily cope with such damage as they have the inherent ability to yield. This is

especially true of impact damage to metals, which is easily detected as the damage starts

on the impacted surface. Whereas in composite laminates, low-energy impact damage is

considered the most serious as it reduces the structural integrity of a structure and

sometimes fractures occur [90]. The fracture process of fibrous composites depends on

their damage tolerance which can be controlled by manipulating the fibre architecture. This

approach does not necessarily restrict the extent of cracking but will control the distribution

of cracks and minimize their effects on the mechanical performance of the structure [86].

1.13 Factors affecting the energy absorption during damage of composite structures

Most of the studies to examine the energy absorbing capabilities of composite materials

have been directed towards the axial crush analysis of the composite thin wall structures.

The energy absorption of composite materials under slow velocity impact is influenced by

different factors like reinforcement material, reinforcement geometry, interphase and

matrix [94]. A fibre reinforced composite consists of two major elements i.e. matrix and

fibre [95]–[98] and the interface region, which is the area of the bond between fibre and

matrix. The type of reinforcing fibre [40], [83], [99]–[104] used in the composite material

determine the energy absorption capabilities of the composite. The certain findings are

[105]:

1- Energy absorption capabilities of the fibre are greater, which has higher strain to failure

ratio.

2- The decrease in density of the fibre results in an increase in specific energy absorption

ability of the fibre.

33

In polymer matrix composites, apart from fibre reinforcement and a polymeric matrix, a

third essential component: interphase could affect the performance of composites [106].

The interphase is a region of finite mass located at the fibre/matrix boundary. The bond

strength between fibre and matrix strongly affect the mechanical properties of composites

[107], [108]. Depending upon the fibre types, composites with poor fibre/matrix interphase

absorb more energy under impact loading because of debonding and delamination.

For 3D orthogonal hybrid woven composites, Luo [109] and Lv [110] tested composite

specimens with hemispherical-ended and flat-ended steel rods. The energy absorption and

damage mechanism were both dependent on the loading rate. Under low velocity impact,

composite failure occurred due to higher tensile and compressive stresses created by the

bending moment. At higher impact loading the damage appeared in the form of matrix

cracking, fibre breakage and fibre pull-out. It was observed that the through thickness

reinforcement prevents delamination of the structure.

The influence of binder volume fraction and the location of binder yarn were studied during

impact for 3D woven carbon fibre composites [111]. Specimens with low binder volume

fraction had a high damage area when compared to specimens with a high binder volume

fraction Similarly, impacts to the edge of the binder were deeper than impacts to the middle

of the binder. So binder location under the impactor had a direct influence on impact depth

[112].

In Padak and Alagirusam’s [113] study of the effect of yarn interlacement on impact

behaviour, they used the interlacement index to represent the interlacement points and

observed that the impact strength of a material increases linearly with the interlacement

index. The yarn interlacement produces binding points which transmit the impact load from

one fibre to other. More interlacement in the preform can reduce fiber failure in the

composite, which is due to a better distribution of the load within the multilayer structure

through the interlacement points; whereas a comparison of different fiber architectures

showed that impact/damage resistance and damage tolerance (the residual strength of the

material following impact damage) properties of 3D woven composites are superior to UD

laminates and 2D non-crimp fabrics [114].

Potluri et al. [115] compared the impact resistance of 3D woven composites at different

energy levels with 2D woven. 3D woven structures exhibited a significantly lower damage

area and higher damage resistance when compared to 2D woven laminates as shown in

Figure 1.27.

34

Figure 1.27 Damage tolerance of different 2D and 3D composite structures [115]

1.14 Compression, compression after impact (CAI) and other mechanical

behaviours of 3D woven solid composite structures

The effect of fabric structure [12], [116], fabric compaction [117] and yarn crimp [118] in

compression has been studied by different researchers. All of them observed that

composites fail in shear, with local yarn buckling and the formation of kink bands.

However, the damage zone depends on the amount of yarn distortion and varies from

structure to structure. The compressive strength of 3D woven structures can be improved

upon, degraded or remain unchanged by through-thickness (z-binder) reinforcement [62],

[119]. Through thickness, yarn does not eliminate delamination during an impact event but

it does suppress both delamination growth (by bridging the delamination crack) and

buckling under subsequent compressive loads, as well as increase interlaminar fracture

toughness. With delamination suppressed, kink band formation (kinking) is the ultimate

failure mechanism [64].

3D woven composites limit delamination significantly by absorbing more energy and thus

possess higher residual compression strength than their respective 2D laminates at the same

impact energy, despite having an undamaged strength less than that of the 2D materials.

The high damage tolerance and energy absorption capability of 3D woven structures are

strongly influenced by the architecture and amount of the through-thickness reinforcement.

Improved residual strength properties can be achieved by using hybrid yarn techniques

[62]. The high damage tolerance and energy absorption capability of 3D woven structures

35

are strongly influenced by the orientation and amount of the through thickness

reinforcement as shown in Figure 1.28.

Figure 1.28 Compression after impact strength of 3D woven composites at different

energy levels [8]

Potluri et al. [115] reported the residual compressive strength properties of 3D woven

structures in comparison to 2D woven. They found that 3D woven composites have a

critical damage width below which there appears no apparent degradation to the

compression strength. It can also be seen that a finer through-thickness reinforcement

improves residual compressive strength by minimizing in-plane yarn distortion [112]. The

compressive failure of 3D woven composites is caused by the same kinking phenomenon

as the 2D laminates, but the failure mechanism is more complex [120]. Demuts and Deo

[121] observed that loss/damage in compressive strength after low velocity impact is higher

than the damage created by drilled holes and that a structure without the appropriate damage

tolerant design may fail due to invisible internal damage occurring without any visible sign

of external surface damage. The retention in residual compressive strength is more than

residual bending stress at the same impact energy, as energy and residual strength decrease

with the increase of impact energy.

Baucom and Zikry’s [122], [123] investigation of the effect of reinforcement geometry (2D

and 3D woven composites) on damage progression and perforation failure, showed that in

the 2D woven laminates damage appears in the form of delamination and fibre breakage on

both the rear and front surfaces of the specimens. In 3D orthogonally, woven composites

36

the spread of radial damage appeared larger on the rear surface of the specimen, with

damage progressing in the form of the straining and fracture of the through-thickness z-

yarns. On the front surface only, fibre debonding and matrix cracking was observed. The

3D woven composites also absorb more energy through the frictional sliding of surface

weft tow through the Z-yarn crimps. The deformation was similar to quasi-static bending

and failure was predicted due to fibre damage at the backside of the composite [124].

Compression after impact (CAI) testing is usually the best way to evaluate the damage

tolerance of composite structures because of its sensitivity to delamination [125]. Damage

Ultrasonic C-scanning, X-radiography and de-ply studies revealed that low-energy impact

on CFRP results in three types of damage: splitting, delamination and broken fibres [126]–

[129]. Zhang et al. [130] studied the compression after impact (CIA) behaviour of low

energy (12J), intermediate (20J) and high energy (32J) impacted plates and concluded that

there was much larger delamination and back face bending failure occur in case of high

energy. The number of impacts had a noticeable effect on the residual compressive strength

of a specimen which included the point of impact. Under repeated intermediate energy

impacts, the residual strength in the adjacent specimen also appeared to be affected [131],

[132].

The undamaged compression strength is controlled by fibre placement, fibre volume

fraction and geometrical defects such as crimp, damage to the fibres, and manufacturing

defects etc. Under a uniaxial compressive load, 3D woven composites fail by kink band

formation in the primary load bearing yarns. Kink band formation is influenced by initial

stuffer misalignment, stuffer buckling, lateral loads imposed by binder yarn, delamination

and the buckling of layers of stuffers (straight yarns along the length of the fabric) and

fillers (straight yarns across the width of the fabric), plus the debonding of individual

stuffers. The initial misalignment and geometrical flaws tend to lower the compressive

strength but cause the damage to be spatially distributed, resulting in a high strain to failure

[9][120]. It was observed that kinking reduced the load carrying capability in the outer layer

yarns, resulting in a 20-35% decrease in compressive strength and stiffness of 3D

orthogonally woven composites. The critical load required for kinking decreased with an

increase of the misalignment angle [119].

In polymer matrix composites, apart from fibre reinforcement and a polymeric matrix, a

third essential component: interface could affect the performance of composites [106]. The

interface is a region of finite mass located at the fibre/matrix boundary. The bond strength

between fibre and matrix strongly affect the mechanical properties of composites [107].

Depending upon the fibre types, composites with poor fibre/matrix interface absorb more

37

energy under impact loading because of debonding and delamination [133], [134]. Potluri

at al. compared the 3D woven, stitched and tufted composites with 50% fibre volume

fraction and revealed that fibre damage and distortion was higher in woven and stitched

composites while interlaminar shear strength was higher in 3D angle interlocked

composites [135]. Dhiman et al. checked the effect of binder yarns on 3D woven

composites by comparing the predicted tensile strength and stiffness of modelled 3D woven

composites with the tested samples data. They found a reasonable agreement between

tested results and simulated stress-strain curves of samples [136] and similar agreement of

tensile results between experimental and numerical data was found by Saleh et al. for 3D

woven orthogonal composites[137].

1.15 Mechanical behaviour of 3D woven spacer composite structures

The 3D spacer fabric composites can offer high skin-core deboning resistance and impact

resistance, excellent durability and superior integrity, high stiffness, excellent thermal

insulation, acoustic damping, and so on [44]. Different researchers had assessed the mono-

spacer fabric composite panels with respect to its drum-peel strength, flatwise compressive

strength and transversal shear modulus [62], [138], [139]. They revealed that a very

significant skin-core debonding resistance exists in the fabric reinforced composites. It has

also been investigated that the pile yarns played a vital role on the flatwise compression

and shear properties. 3D hollow structures and 3D integrated laminates core filled with

foam were analysed by M. V. Hosur et al. [140], [141]under low-velocity impact response.

M. Li. et al. [44] investigated the mechanical performance of corrugated and 8-shape piles

spacer structure and revealed that corrugated piles showed much bigger anisotropic

behaviour as compared to the 8-shaped pile structure. Furthermore, the mono-spacer fabric

composites failed under flat compressive load due to the broken or slanted piles, and the

performance would be optimized at pile angle of 80°–90°. Whereas piles cracked at its

endpoints under shear load, while during edgewise compression test mono-spacer fabric

composite failed by the facesheet wrinkling.

Flat compression properties were decreased with the increase of core heights and the flat

load-displacement curves exhibited obvious elastic, plasticity plateau and densification

stage while the warp compression properties increased with the increase of core heights

and only the elastic stage was obvious for the flat load-displacement curves. Moreover, the

flat compression properties were superior to the warp compression in the value as shown

in Figure 1.29 [142].

38

Figure 1.29 variation of flat compression properties with core height [142]

The flexural experiment of 3D spacer composite having a thickness of 4 mm for facesheet

showed that the thick face sheets could enhance the bending load resistance capacity

significantly [143]. Impact energy increased and damage of composite reduced with the

increase of core heights (5 mm,10 mm, 15 mm, 20 mm, 25 mm, 30 mm) at both room and

liquid nitrogen temperatures [45]. Quasi-static compression of glass/ethoxylene 3D spacer

composite showed the tilting of the fibre piles initially which leads to the simultaneous

deformation of the cores by compression and shear. After the elastic buckling of the curved

piles, there is a plastic rotation of the piles which enables the deformation with a long stable

plateau. While in three-point bending, the failure of a thicker panel was dominated by the

crippling and shear failure within the skins [144].

1.16 Summary of literature

Damage or failure of the composite structures during different mechanical loads is an

important issue in high performance engineering structures like automobiles and aerospace

industry. The damage sustained by a composite during different forms of mechanical

loading is a function of its 2D and 3D reinforcement. This literature survey highlights the

effect of different 3D woven (solid and spacer) fabric structures on the mechanical

properties. It also highlights the delamination problem associated with 2D woven laminates

as well as the potential of 3D woven composites at improving delamination resistance and

interlaminar properties. limited research has been conducted on the hybrid interlock 3D

woven solid composite structures under different mechanical loads and cyclic loading of

the 3D woven spacer composites.

39

1.17 Problem definition

Mechanical performance of composites like flexural strength, impact strength, damage

resistance and damage tolerance are important issues in the service environment for

automobiles, airframes and other high-performance engineering structures. In order to

improve the above stated composite problems, a high level of through thickness and

interlaminar strength is required. 3D woven composites impart superior mechanical

performance as compared to 2D laminates. They resist delamination and their through

thickness properties are better as compared to the 2D laminates.

Metals (steel, aluminium alloy) and plastics are used in automobiles industry. Metals have

high weight and cost, resulting in the decrease in fuel efficiency and an increase of carbon

dioxide content in the environment. While plastics showed less strength as compared to the

metals. To cover the issues of higher weight, cost and strength fibre reinforced composites

(FRC) are focused, but two dimensional (2D) FRC showed poor delamination resistance

and through thickness properties. To deal with these drawbacks three-dimensional (3D)

fibre reinforced composites are preferred in high performance applications like

automobiles. The practical utilization of 3D woven composites to structural components

requires the understanding and characterization of different mechanical properties.

In a high-performance application, 3D woven (solid and spacer) composites are used

undergo different types of static and dynamic loadings. A substantial amount of

experimental work has been performed to understand the in-plane properties as well as the

out of the plane performance of 3D woven composites exposed to different mechanical

loads. Maximum literature is available on the 3D warp interlock woven composite

structures. However, very rare work found of the 3D woven weft, bidirectional and hybrid

interlock composite structures. Using the 3D bidirectional interlock woven structures crimp

percentage can be balanced both in warp and weft direction instead of the major difference

in crimp of individual warp and weft interlock. Also using the hybrid binding yarns

interlocking pattern mechanical properties can also be improved in comparison with four

basic type of 3D weaving.

Influence of individual 3D warp and weft interlocks and their combination (bidirectional

interlock) with hybrid 3D interlocking on the in-plane, as well as the out of plane properties

of different 3D woven composites with extra stuffer yarns and, time dependent performance

of the 3D woven spacer composites, has not yet been explored.

1.18 Objectives

The primary objective of this research is to optimize 3D woven reinforcements (solid and

spacer) with improved in-plane and out of plane mechanical properties for high

40

performance applications like automobiles industry. In addition to this, the effect of weave

patterns (modification in both binder path, binder type and binder float length) is also

studied.

For this purpose, the following objectives have been set:

1. Design and fabrication of warp, weft and bidirectional interlock 3D woven

composite structure using the orthogonal layer to layer 3D multilayer.

2. Design and fabrication of 3D woven warp interlock composite structures using the

orthogonal layer to layer (OLL), orthogonal through the thickness (OTT), Angle

layer to layer (ALL), angle through thickness (ATT) interlocking and their

combination with extra stuffer yarns in the warp direction.

3. Investigation of the influence of interlocking patterns and binder yarns on the

mechanical properties of the 3D woven composites in both warp and weft

directions.

4. Fabrication of the 3D woven spacer composites with different thickness levels and

their influence on the mechanical as well as on the time dependent/dynamic

compression/recovery properties.

To achieve the above-mentioned objectives, work is divided into three parts/stages as

mentioned in Figure 1.30.

Figure 1.30 Flow chart of the study

Details of three different parts/stages are given below;

3D woven composites

3D woven solid composites

1-Influence of interlocking patterns on mechanical

performance of novel 3D woven composites

2-Effect of Z-binder yarn on the mechanical

performance of hybrid 3D woven composites

with stuffer yarns

3D woven spacer composites

3- Effect of pile height on compression/recovery

properties of 3D woven spacer fabric reinforced

composites

41

1- Influence of interlocking patterns on mechanical performance of solid 3D novel

woven composites

Reinforcement material and type matrix

Glass filament yarn 10K denier and 7200 denier carbon tow having 12K filaments are in

warp and weft directions respectively while the two-part epoxy resin is used for composite

fabrication using vacuum bag moulding.

Types of 3D woven solid structures

Three different types of solid 3D woven structures are produced on rapier dobby loom

which are given below;

1. Orthogonal layer to layer warp interlock

2. Orthogonal layer to layer weft interlock

3. Orthogonal layer to layer bidirectional (combination of warp and weft) interlock

Characterizations

Four different types of mechanical characterizations of the produced composites structures

are done to check their performance which are given below;

1. Tensile properties (ASTM D3039)

2. Flexural properties (ASTM D7264)

3. Impact properties (ISO 179)

4. Dynamic mechanical analysis (ASTM D7028)

2- Effect of Z-binder yarn on the mechanical performance of hybrid 3D woven

composites with extra stuffer yarns

Reinforcement material and type of matrix

Jute yarn of 2500 denier (278 tex) is used both in warp and weft directions while the green

epoxy resin (CHS-EPOXY G530) is used for composite fabrication using compression

plates.

Types of 3D woven solid structures

Seven different types of solid 3D woven structures are produced on rapier dobby loom


1. Layer to layer (LL) Orthogonal interlock (O) with warp stuffer yarns in warp

direction

2. Through thickness (TT) Orthogonal interlock (O) with warp stuffer yarns in warp

direction

3. Layer to layer (LL) Angle interlock (A) with warp stuffer yarns in warp direction

4. Through thickness (TT) Angle interlock (A) with warp stuffer yarns in warp

direction

42

5. Combination of Through thickness (TT) Orthogonal interlock (O) and Through

thickness (TT) Angle interlock (A) interlocking patterns with warp stuffer yarns in

warp direction

6. Combination of Through thickness (TT) Orthogonal interlock (O) and Layer to

layer (LL) Angle interlock (A) interlocking patterns with warp stuffer yarns in warp

direction

7. Bidirectional interlock (Combination of warp and weft interlock)

Characterizations

Six different types of mechanical characterizations of the produced composites structures


1. Tensile properties (ASTM D3039)


3. Short beam strength (ASTM D2344)

4. Charpy impact tester (ISO 179)

5. Drop weight impact tester (ASTM D 7136)

6. Compression after impact (ASTM D7137)

3- Effect of pile height on compression/recovery properties of 3D woven spacer

fabric reinforced composites

Reinforcement material and type matrix

Glass filament (264 tex) yarn is in warp, weft and pile directions while green epoxy (CHS-

EPOXY G530) is used for composite fabrication using hand lay-up/spray-up technique.

Types of 3D woven spacer structures

Only one type of 3D woven spacer structures is used with three different thickness levels


1. 4mm thick

2. 10mm thick

3. 20mm thick

Characterizations

Five different types of mechanical characterizations of the produced composites structures


1. Slow penetration (puncture test, EN 388)


3. Flat compression (ASTM C365)

4. Low velocity impact properties (ASTM D 7136)

5. Single and multi-cycle compression and recovery test (ASTM F36)

43

Chapter # 2

3D Woven Solid Composite Structures

(Part A)

44

2 Influence of interlocking patterns on mechanical performance of

novel 3D woven solid composites

An experimental investigation of the mechanical behaviour of three-dimensional (3D)

orthogonal layer to layer (LL) interlock composites is discussed in this chapter. The glass

filament yarn and carbon tows were used as reinforcement in warp and weft directions

respectively, whereas epoxy was used as the resin for composite fabrication. Three different

types of the orthogonal layer to layer interlock: warp, weft and bidirectional composites

were fabricated and the effect of interlocking pattern on their mechanical performance was

evaluated. The evaluation of mechanical performance was made on the basis of tensile

strength, impact resistance, flexural strength and dynamic mechanical analysis (DMA) of

composites in warp and weft directions. It was found that warp and weft interlock

composites showed better tensile behaviour as compared to bidirectional interlock

composite in warp and weft direction, due to the presence of less crimp as compared to

bidirectional interlock. However, the bidirectional interlock composite exhibited

considerably superior impact resistance and three-point bending strength as compared to

the other structures under investigation. These superior properties of bidirectional interlock

composites were achieved by interlocking points in warp and weft directions

simultaneously, creating a more compact and isotropic structure. Tan delta values of DMA

results showed that bidirectional interlock displayed the highest capacity of energy

dissipation in warp and weft directions while weft interlock structures displayed highest

storage and loss moduli in the warp direction.

2.1 Introduction

Two-dimensional (2D) woven structures have substantial length and width with very small

thickness, while multilayer interlock (3D) structures have a significant value of thickness

too. Such fabrics are produced with the yarns oriented along the X-axis (longitudinal), Y-

axis (cross) and Z-axis (vertical) [15], [145]–[148]. The 2D structures generally serve as

reinforcement for laminated composites, which have optimal in-plane performance but

their out-of-plane properties are poor [149]. The multilayer interlock structures have Z

yarns along thickness, which provide the strength and stiffness in out of plane direction.

Therefore, composites reinforced with multilayer interlock structures show excellent

performance properties as compared to 2D fabrics [150].

The multilayer interlock structures are categorized [34], [35] as an orthogonal interlock and

angle interlock depending on the crossing pattern of yarns, which may be layer to layer

(LL) interlock or through thickness (TT) interlock. The layer to layer orthogonal interlocks

showed better mechanical performance as compared to their through thickness counterparts

45

both at reinforcement and composite level [151]. Another classification system categorizes

the multilayer interlock structures into warp and weft interlock, based on the yarn that

interlocks the layers (either warp or weft). In LL orthogonal structures, tensile strength and

rigidity of structure increase with the number of layers, while in LL angle interlock

structures, tensile strength, tensile stiffness and bending rigidity increase in weft direction

with an increase in a number of layers but remain same in warp direction [152], [153].

Similarly, hybrid woven structures can be made by combining any of the four basic types

3D structures i.e. (Orthogonal layer to layer, Orthogonal through thickness, layer to layer

angle interlock and through thickness angle interlock) to get required mechanical

performance depending upon the target applications [9], [41]–[43].

Huang and Zhong [26] compared the elongation at break during tensile testing of four

different types of 3D woven composites and revealed that to get a dimensionally stable and

mechanically strong composite, the straight arrangement of yarns/filaments would be

preferred and hybridization would also affect the effective stiffness and strength during

tension [40].

Through thickness (TT) angle interlock, carbon/epoxy composite showed better

compressive and flexural strength as compared to the TT orthogonal interlock but longer

delamination crack and tensile strength were affected by waviness of load bearing fibres

[154] and architecture [155], [156]. The TT composites prevent the delamination with the

long cantilever bending tests, and provide measured and limited changes in post-peak load

response under short beam tests. Localized delamination was found in these tests, however,

in long beam testing, the failure mechanism was in the form of compressive buckling of

longitudinal fibres and large tensile cracks at the clamping end [157].

Furthermore, in 3D orthogonal TT carbon/epoxy composites, Young’s modulus and

average failure strength in the weft yarn direction was larger than that in the stuffer yarn

direction, while the average failure strain in the filler yarn direction was less than that in

the stuffer yarn direction [158]. Among the 3D woven carbon/epoxy composites

(orthogonal, layer-to-layer, angle interlock), 3D orthogonal woven composites showed the

best performance (highest failure strength and failure strain, high energy absorption) under

off-axis loading due to the interlocking mechanism provided by z-binder. This interlocking

mechanism increases the rotation angle of warp and weft yarns, and thus the ability of the

yarns to bear extensive off-axis strain [159]. The energy absorption capability of a structure

is mainly affected by the presence of fibres or yarns in the thickness direction. The 2D

laminates composites absorbed (14–26%) less energy than the 3D composites, while 3D

angle interlock displayed higher peak load (14.21–30.25%), more energy absorption (12.7–

46

26.2%) and lower cone formation at the back of target (25–39%) as compared to 3D

orthogonal and 2D laminated composites [160].

In plane shear (strength) and modulus of multiaxial 3D woven carbon/epoxy composites

were better in comparison with 3D orthogonal woven carbon/epoxy composites. However,

interlaminar shear strength, bending strength, and bending modulus of the multiaxial 3D

woven composite was lesser than that of 3D orthogonal woven composites because of the

alignments of +/-bias yarns on both surfaces of multiaxial 3D woven structures [161]. The

mode I interlaminar fracture toughness of 3D woven through thickness glass/epoxy

composites increased rapidly with the increase of z-binder yarns. The interlaminar

toughness was increased fourfold with the z-binder content of just 1.1% by volume and

delamination resistance as well [162]. The energy absorption ability and failure load of 3D

orthogonal hybrid composites increased with the increase of impact velocity. The damaged

composites morphologies showed the different failure modes under high velocity and

quasi-static impact tests. [109], [110]. 3D woven composites absorbed 25% more impact

energy and 12-18% more breaking load as compared to the 2D woven composites[163].

Also, 3D woven composites showed a higher storage modulus[164].

Shallow bend joint quartz/silica composite had a higher flexural strength, shear strength,

and fracture toughness than 3D orthogonal quartz/silica composite, while the pull-out

length of fibres of 3D orthogonal quartz/silica composite was shorter than that of shallow

bend joint composite [165]. Comparison of different 3D woven composites displayed

different results, angle interlock composites possess the highest value of stress followed by

the warp interlock and orthogonal based composites [166]. 3D orthogonal structures were

difficult to compress to a specific fiber volume fraction due to the presence of vertically

downward tows, while layer-to-layer (warp interlock) structure was less stiff in through

thickness direction due to the fact that the z-fibers in layer to layer (LL) assembly were less

perpendicular, thus hardening the structure less in the Z-direction [167]. The load-time,

displacement–time and load-displacement curves during low velocity impact, allowed to

identify a critical threshold energy for the composite material perforation [168]. 3D (X-ray

tomography) imaging of 3D LL and angle interlock (AI) showed that higher crack density

was found in the angle interlock composite than the layer to layer composite. Transverse

cracking initiates in the fibre-rich regions of weft yarns rather than the resin rich regions

[169] and greatly affected by void volume fraction [170].

This is evident from the literature that interlocking pattern greatly affects the performance

properties of the multilayer interlock fabric based composites. Most of the reported studies

are on the properties of 3D fabrics and composites made using multilayer interlock fabric

47

in which binding pattern is mostly in the warp direction. Tows/yarns in the resultant fabric

have more crimp in the warp direction and negligible crimp in the weft direction. Therefore,

fabric/composite don’t have balanced (equal in warp and weft direction) mechanical

properties. The mismatch of mechanical behaviour may cause structural instability and

additional stresses in the composite structure. One of the possible solutions to made

balanced 3D fabric is to develop a hybrid 3D woven fabric with interlocking in both warp

and weft direction. To the best of our knowledge, no significant work has been reported on

this subject. In this study, three different types of the 3D orthogonal layer to layer interlock

composites were produced and their effect on mechanical performance was evaluated.

2.2 Experimental

2.2.1 Reinforcement preparation

Glass filament of 10K denier as warp yarn, whereas the carbon tows of 7200 denier having

12K number of filaments were used in the weft direction to produce 3D orthogonal layer

to layer interlock fabric structures/reinforcements. The glass filament yarn was sized using

a single end sizing machine with 2% solution of polyvinyl alcohol (PVA). The sizing

helped to adhere the filaments together and to reduce abrasion with loom parts during

production.

Three types of the 3D orthogonal layer to layer interlock fabric structures i.e. warp

interlock, weft interlock and bidirectional (weft and warp combined) interlock, were

developed on a rapier dobby loom with little modifications according to each weave design.

Weave designs of the 3D orthogonal layer to layer warp, weft and bidirectional interlocks

are given in APPENDIX 2.1, APPENDIX 2.2 and APPENDIX 2.3 respectively. In warp

interlock fabrics, to stitch/interlock different fabric layers, only warp threads stitch between

the layers (as per specified pattern), weft threads have nothing to do with this

stitching/interlocking. The pattern of stitching by warp threads is controlled by the shedding

of warp threads [24]. While in weft interlock fabrics [171], to stitch/interlock different

fabric layers, only weft threads stitch between the layers (as per specified pattern), warp

threads have nothing to do with this stitching/interlocking. For weft interlock, shedding for

the weft threads is not required as a pattern of stitching by weft threads is controlled by

shedding of warp threads. Weft interlock structures were discussed by X. Chen [172] and

concluded that the manufacturing speed of weft interlock woven structures (in terms of

fabric length produced) is quite low, it proportionally decreases with the increase in fabric

width and thickness. A similar concept for the production of weft interlock structures was

also discussed by Miller et al. [173], [174] in his patents.

48

Warp interlock fabric structure is generally tighter in comparison with weft interlock

fabrics as the tension of warp stitching threads (in warp interlock fabric structure) is higher

than weft stitching threads (in weft interlock fabric structure). Furthermore, in warp

interlock fabrics, warp yarns are undulated whereas weft yarns almost lay straight. Whereas

in weft interlock fabrics, warp yarns are slightly undulated (due to the higher tension in

warp) whereas stitching weft yarns are highly undulated. Additionally, weft interlock

structure is of significant interest, because it minimizes crimp in the longitudinal direction

of the fabric [172]. Also, in bidirectional interlock, undulation/crimp percentage would be

highest due to the alternate stacking of both weft and warp interlocks. All the structures

had four layers of density 140 ends/10cm (warp) and 100 picks/10cm (weft). Cross

sectional views of warp and weft interlock structures are shown in Figure 2.1(a) and Figure

2.1 (b) respectively designed in TexGen software [175], while bidirectional interlock

structure was developed in such a way that warp and weft interlocks were stacked and

stitched one over the other in an alternative sequence as shown in Figure 2.1(c).

Figure 2.1 Cross sectional views of the orthogonal layer to layer (a) warp interlock, (b)

weft interlock and (c) schematic view of the bidirectional interlock

Before fabricating the composites, desizing of all the woven reinforcements was done with

hot water to dissolve PVA from glass yarn to avoid the fibre–matrix interface problem.

Bi-directional Interlock (c)

Warp Interlock Weft Interlock

Weft Interlock Warp Interlock

49

2.2.2 Composite fabrication

Two-component epoxy resin i.e. part A (liquid) and part B activator (solid powder) was

used for fabrication. The gelation time for this resin was 25 minutes at 150 °C and Tg was

122 °C. The composites were fabricated using a vacuum bag moulding technique. The resin

was applied to the reinforcement by hand lay-up. The structure was then sealed in an air

tight bagging film, and vacuum was generated (negative pressure of one bar) inside this

film. It gave an evenly distributed pressure on the surface; consolidating the structure by

removing air and voids. The fibre volume fraction of all the samples was maintained to

45%. Fibre volume fraction was calculated by the formula given in Equation 1.1.

The initials curing took place at room temperature for 24 hours, followed by post curing at

120 °C for 3 hours in hot plates. Post curing was done to assure the complete cross-linking

of resin.

2.2.3 Characterization

Each of the 3D composite samples was characterized in warp and weft direction. The

notations used for the samples are given in Table 2.1.

Table 2.1 Notation for composite structures

Sr. # Type of 3D multilayer

composite Test Direction Notation

1 Warp Interlock

Composite

Warp wise 1P

2 Weft wise 1W

3 Weft Interlock

Composite

Warp wise 2P

4 Weft wise 2W

5 Bidirectional Interlock

Composite

Warp wise 3P

6 Weft wise 3W

The performance of developed composites was investigated in terms of mechanical

properties (tensile, impact, flexural properties and DMA). Universal Tensile Strength

Tester, with standard test method ASTM D3039 was used to test the tensile properties of

composites on specimens of size 250 mm long and 25 mm wide. The tensile modulus was

calculated by the difference between the stresses of two strain point to the difference

between two selected strain points. Three-point bending test (for flexural strength) was also

performed on the same equipment as per ASTM D7264 on specimens of size 120 mm long

50

and 13 mm wide. The span length to thickness ratio of the specimen was 32:1 while its

width was 13 mm. The maximum force and deflection at maximum force were used to

calculate the flexural strength. While pendulum impact tester (Charpy impact tester) was

used for the impact strength of composite samples following the standard test method ISO

179 on specimens of size 80 mm long and 10 mm wide. Dynamic mechanical analysis

(DMA) tests of the composite samples were performed using the Q800 DMA TA

instrument. The DMA results i.e. loss modulus, dynamic modulus and tan delta of the three

composite samples both in warp and weft direction were calculated. Dual cantilever test

was performed using the standard test method ASTM D7028. Dynamic properties were

measured in the temperature range of 0 to 150˚C with the heating rate of 2˚C min˗1. Each

testing was repeated three times for every sample and an average of the results were

reported.

2.3 Results and discussion

As discussed earlier, the mechanical characterization was performed for all the samples

both along warp and weft. The comparison of the individual properties is given in the

subsequent sections.

Optical images showing cross section and fibre-matrix interface of the 3D orthogonal layer

to layer interlock composite structures have been given in Figure 2.2. Four layers of

structure can be observed from the images. The white coloured yarns running along the

length of composites are the glass filaments in the warp direction, while the black yarns

represent the carbon tow in the weft direction of three samples. The images showed that a

good fibre-matrix interface exists in all the composite samples.

Figure 2.2 Optical images showing cross section and fibre-matrix interface of the

orthogonal layer to layer interlock composites

The fibre-matrix interface strength greatly affects the energy absorption and final

performance of the composite structures under mechanical loading [176], [177]. For any

brittle-fibre/brittle-matrix composite, the higher strength required a strong interfacial bond,

51

but this may lead to a low fracture energy absorption. However, by proper control of

physical and mechanical properties of the fiber-matrix interface, high strength

characteristics can be combined with higher toughness [178].

2.3.1 Tensile Properties

The tensile properties, including tensile strength, tensile modulus and the extension at break

of the composite samples are given in Table 2.2.

Table 2.2 Tensile properties of composite structures

Sr. # Notation Extension at

break (%)

Tensile

strength

(MPa)

Tensile

modulus

(GPa)

1 1P 4.03 ± 0.03 135.69 ± 1.70 1.04 ± 0.02

2 1W 3.74 ± 0.02 143.60 ± 1.80 3.55 ± 0.08

3 2P 3.02 ± 0.02 149.87 ± 1.95 1.15 ± 0.03

4 2W 4.23 ± 0.03 139.07 ± 1.75 3.78 ± 0.09

5 3P 5.81 ± 0.03 112.07 ± 1.60 0.95 ± 0.02

6 3W 5.24 ± 0.03 123.73 ± 1.70 3.08 ± 0.06

In the comparison of the tensile behaviour of warp, weft and bidirectional interlocks; it was

found that warp and weft interlocks showed the comparable results of extension at break,

tensile modulus and tensile strength. Within the warp interlock composite structure, the

tensile strength was higher in weft direction and extension at break percentage was higher

in the warp direction. It was due to the crimp percentage affecting the extension at break

and tensile strength of the structure; if the value of crimp is higher in the structure, initial

force will be consumed to straighten the crimped yarns in that direction resulting more

extension at break and low tensile strength [179]–[181] and vice versa. In warp interlock

structure, crimp percentage was higher in the warp direction subsequent less tensile strength

in that direction. While within the weft interlock structure, the tensile strength was higher

in warp direction and extension at break was lesser in that direction, because crimp

percentage was higher in weft direction as shown in Figure 2.3(a) and Figure 2.3(b).

52

Figure 2.3 Comparison of (a) tensile strength and (b) elongation at break (%) of the

composite structures

Furthermore, in weft interlock tensile strength in weft direction was not dropped so much

in presence of crimp in weft direction due to the presence of high strength of carbon tow in

the weft direction. Since glass filament yarn was used in the warp direction and carbon tow

was used in the weft direction, that’s why in warp direction tensile modulus was lesser in

all the samples as compared to the weft direction as shown in Table 2.2. Moreover,

bidirectional interlock showed inferior tensile behaviour both in warp and weft direction in

comparison with warp and weft interlock. Because, in bidirectional interlock composite

structure, both in warp and weft direction crimp percentage was higher, resulting in more

0

20

40

60

80

100

120

140

160

1P 1W 2P 2W 3P 3W

Ten

sil

e s

tren

gth

(M

Pa)

3D orthogonal layer to layer interlock structures(a)

Warp interlock Weft interlock Bidirectional

interlock

0

1

2

3

4

5

6

7

1P 1W 2P 2W 3P 3W

Ex

ten

sio

n a

t b

re

ak

(%

)

3D orthogonal layer to layer interlock structures(b)


interlock

53

extension at the break and lesser tensile strength. In bidirectional interlock structure as

shown in Figure 2.1(c), warp and weft interlocks were stacked one over the other

alternately, consequentially crimp percentage became more in warp and weft direction.

A similar trend of tensile modulus was found in warp and weft direction of all the interlock

composites. In bidirectional interlock, tensile modulus was lesser in warp and weft

direction due to the presence of higher crimp percentage as compared to the warp and weft

interlock composites. Tensile strength of 3D composite structures was also statistically

significant, because P value was less than 0.05 as highlighted in Table 2.3 of ANOVA

results. 3D woven structures showed significant effect on tensile strength of composite

structures.

Table 2.3 ANOVA results for tensile strength of composite structures

Source DF Adj SS Adj MS F-Value P-Value

Factor 2 2167.03 1083.53 373.18 0.000

Error 6 17.42 2.90

Total 8 2184.45

2.3.2 Impact properties

The impact strength of all glass-carbon/epoxy composite samples were characterized by

Charpy impact tester and their mean values of impact strength are plotted in Figure 2.4.

The key element of consideration in impact strength results are the interlocking pattern,

crimp and compactness of the structure. The 3D systems provide an inherent capability to

dissipate energy over a larger area than 2D woven systems with similar fibre volume

fraction [66].

Figure 2.4 Comparison of the impact strength of the composite structures

0

20

40

60

80

100

120

140

160

180

Imp

act

str

en

gth

(K

J/m

2)

3D orthogonal layer to layer interlock structures


interlock

54

The impact strength of all the samples was calculated by using the dissipated energy and

area of the tested samples. This damage tolerance in 3D woven composites is due to unique

energy absorption behaviour, which involves the crimped portion of z-tows/yarns in the 3D

composites [182]. The impact strength of both warp and weft interlock composites was

comparable both in warp and weft directions. It was due to the usage of same yarn counts

and thread densities in warp and weft directions respectively and an insignificant difference

in crimping behaviour of both the samples. At the same time, compactness of both the

structure is comparable in the cross-sectional views of warp and weft interlocks. In warp

interlock, glass filament yarns were Interlocking all the layers together while carbon was

used in the weft direction, resulting in more crimp in glass yarns as compared to the carbon

tow in the weft direction and glass yarns were in the z-direction, bearing more impact

energy in warp direction as compared to the weft direction. Similarly, in weft interlock,

carbon tows were interlocking the whole layers together in the z-direction, bearing more

impact energy in the weft direction as compared to the warp direction as shown in Figure

2.4.

While in the bidirectional interlock, impact strength was higher as compared to both warp

and weft interlocks due to an increase in a number of z-directional yarns i.e. warp and weft

interlocks were stacked one over the other so both carbon tow and glass filament yarns

were found in the z-direction. More the number of yarns in the weft direction, higher will

be the energy absorbed by the structure and higher will be their corresponding impact

strength [183]. At the same time crimp percentage was higher in bidirectional interlock due

to the stacking of interlocks both in the warp and weft direction, resulting in more damage

tolerance and more energy dissipation in the z-direction. Within the bidirectional interlock,

both in warp and weft directions there was no major difference in the impact strength as

shown in Figure 2.4, due to the presence of similar crimp percentage and number of z-

direction yarns in both directions. A similar response was found by Richardson et al. [184]

and Aiman et al. [185] and reported that 3D composites could withstand a prolonged

expose, as the Z-yarn ability had resulted in the increase of impact energy absorption and

wider impact force dissipation.

2.3.3 Flexural properties

Three-point bending test was performed on all the samples in both warp and weft directions

and results are given in Table 2.4. Flexural performance results of three different types of

the orthogonal layer to layer interlock: warp, weft and bidirectional composites, which were

compared both in warp and weft direction and found different results in three samples in

both warp and weft direction.

55

Table 2.4 Maximum deflection and maximum force during flexural testing of structures

Notation Maximum Deflection

(mm)

Maximum Force

(N)

1P 14.65 ± 0.08 128.98 ± 1.52

1W 17.00 ± 0.10 305.48 ± 2.03

2P 13.25 ± 0.07 146.79 ± 1.60

2W 21.96 ± 0.11 286.06 ± 1.95

3P 12.82 ± 0.06 220.78 ± 1.70

3W 16.56 ± 0.09 388.48 ± 2.59

In warp, weft and bidirectional interlock, maximum force and deflection values were higher

in weft direction as compared to the warp direction. While, within the warp and weft

interlocks maximum force values were comparable but, deflection value was higher in weft

interlock in weft direction due to the interlocking pattern of weft interlock. It showed that

warp interlock sample was broken bearing less deflection value and weft interlock elongate

more in the weft direction.

In bidirectional interlock, maximum force bearing values were higher both in warp and

weft direction in comparison with warp and weft interlock. It was due to the stacking

sequence of bidirectional interlock as already shown in Figure 2.1(c). While in weft

direction it bears more load as compared to the warp direction due to the presence of carbon

tow in the weft direction. Maximum deflection values in bidirectional interlock before

rupture point were lower in comparison with warp and weft interlocks in both directions.

Bidirectional interlock elongates less due to the presence of interlocking yarns in both

directions, those try to compensate their extension in opposite directions

Figure 2.5 Load versus elongation graph of the composite structures during flexural

testing

0

50

100

150

200

250

300

350

400

450

0 5 10 15 20

Lo

ad

(N

)

Elongation (mm)

1P 1W 2P 2W 3P 3W

56

Maximum load against elongation taken during breakage for all samples was plotted in

Figure 2.5 for further understanding of breakage behaviour.

Furthermore, Flexural strength and flexural modulus values of bidirectional interlock were

better than warp and weft interlocks as shown in Figure 2.6(a) and Figure 2.6(b). Flexural

strength and a flexural modulus of warp and weft interlocks were comparable both in warp

and weft direction because the number of interlocking points were almost the same in both

directions. Although, in the weft direction of both warp and weft interlocks, the flexural

strength and flexural modulus were higher due to the presence of high strength carbon tow.

Figure 2.6 Comparison of (a) flexural strength and (b) flexural modulus of the composite

structures

0

100

200

300

400

500

600

700

1P 1W 2P 2W 3P 3W

Fle

xu

ral str

en

gth

(M

Pa)

3D orthogonal layer to layer interlock structures(a)


interlock

0

1

2

3

4

5

6

7

8

1P 1W 2P 2W 3P 3W

Fle

xu

ral m

od

ulu

s (

GP

a)

3D orthogonal layer to layer interlock structures(b)


interlock

57

In bidirectional interlock, flexural strength and modulus values were higher in both warp

and weft direction due to the presence of more number of interlocking points, making it

more compact structure. While in weft direction flexural strength and modulus were higher

due to the presence of interlocking carbon tows. The flexural performance of warp and weft

interlock composites was comparable with each other but bidirectional interlock showed

better flexural performance as compared to the warp and weft interlock composites due to

the compactness of the structure. Flexural strength of 3D composite structures was also

statistically significant, because P value was less than 0.05 as highlighted in Table 2.5 of

ANOVA results. 3D woven structures showed significant effect on flexural strength of

composite structures.

Table 2.5 ANOVA for flexural strength of composite structures


Factor 2 16853.2 8426.58 600.35 0.000

Error 6 84.2 14.04

Total 10 16937.4

2.3.4 Dynamic mechanical analysis (DMA)

The dynamic mechanical analysis is a high precision method for determining the

viscoelastic behaviour of materials. Most of the real-world materials display mechanical

responses that are a mixture of viscous and elastic behaviour [166]. Dynamic mechanical

analysis technique divides the dynamic modulus of materials into two distinct parts: an

elastic (storage modulus) component and viscous (loss modulus) component. Storage

modulus is the component of the dynamic modulus, where the strain is in phase with the

applied stress, and loss modulus is the component of the dynamic modulus, and where the

strain is 90° out of phase with the applied stress. The ratio of loss to storage modulus gives

the tangent of the phase angle delta, and tan delta is known as the damping which is a

measure of energy dissipation [186], [187]. The storage modulus, loss modulus, and tan

delta values of composite samples both in warp and weft directions are plotted against

temperature and are given in Figure 2.7, Figure 2.8 and Figure 2.9 respectively.

The storage modulus values were changed with the change of the interlocking pattern of

the reinforcement and with the increase in temperature as shown in Figure 2.7. The storage

modulus of the weft interlock composite structure in warp direction was higher in

comparison with other composite samples. It was due to the crimp percentage in the

structure. In weft interlock structure, crimp percentage was higher in weft direction as

58

compared to the warp direction. Resulting in more energy storage in warp direction in

comparison with the weft direction.

0 20 40 60 80 100 120 140 160

0

2000

4000

6000

8000

10000

12000

14000

Sto

rage

Mod

ulu

s (M

Pa)

Temperature (oC)

1P

1W

2P

2W

3P

3W

Glassy State Transition

Rubbery State

Figure 2.7 Storage modulus as a function of temperature

While in warp interlock composite structure, storage modulus value was higher in the weft

direction, resulting more energy storage in weft direction as compared to the warp direction

due to the presence of carbon tow and less crimp percentage in the weft direction.

Furthermore, bidirectional interlock composites showed less value of storage modulus in

warp and weft direction as compared to the warp and weft interlock composite samples.

Bidirectional interlock samples had more crimp both in warp and weft directions than

others triggering less energy storage, whereas bidirectional interlock composites showed

the higher value of storage modulus in warp direction as compared to the weft direction,

which means more energy storage in the warp direction. Overall, storage modulus was

higher in warp direction compared to the weft direction both in weft and bidirectional

interlock composites, whereas, in warp interlock structure storage modulus values were

comparable both in warp and weft directions. Furthermore, an increase in temperature

caused a reduction in storage moduli of all the samples [188]. The behaviour of a decrease

in storage moduli with the increase in temperature was similar in all samples as shown in

Figure 2.7 because of the same material in reinforcement and epoxy resin was used for

composite manufacturing.

Moreover, the loss modulus of the weft interlock composite structure in warp direction was

also higher in comparison with other samples in both directions as shown in Figure 2.8.

59

While within the weft interlock structure, crimp percentage was higher in weft direction as

compared to the warp direction resulting more energy dissipation in warp direction in

comparison with the weft direction.

0 20 40 60 80 100 120 140 160

0

200

400

600

800

1000

1200

1400

1600

1800

2000

L

oss

Mod

ulu

s (M

Pa)

Temperature (oC)

1P

1W

2P

2W

3P

3W

Glassy State Transition

Rubbery State

Figure 2.8 Loss modulus as a function of temperature

Warp interlock composite structures showed the intermediate value of loss modulus both

in warp and weft directions between the weft and bidirectional interlock composite

structures. While bidirectional interlock structures showed the lowest value of loss modulus

showing less energy dissipation as compared to the others. Bidirectional interlocks

contained the higher value of crimp percentage in both directions due to the stacking of

warp and weft interlocks one over the other alternately, resulting in less energy dissipation.

Weft interlock structures in warp direction showed better energy storage (storage modulus)

and energy dissipation (loss modulus) at the same time in comparison with all other

structures. The effect of temperature on loss modulus was similar in all the samples because

of the same material used during composite manufacturing. At elevated temperature loss

modulus values were decreased [188] and became almost zero in all the samples as shown

in Figure 2.8.

The variation in tan delta as a function of the temperature is shown in Figure 2.9 revealed

that tan delta value decreased and became zero at elevated temperatures [189]. A higher

value of tan delta specified that material had more energy dissipation potential while the

60

decreased value of tan delta showed that your material behaviour was more elastic and store

more energy when the load was applied on it rather than dissipating energy [190].

0 20 40 60 80 100 120 140 160

0.0

0.1

0.2

0.3

0.4

0.5

Tan

delt

a

Temperature (oC)

1P

1W

2P

2W

3P

3W

Glassy State

Transition

Rubbery State

Figure 2.9 Tan delta as a function of temperature

Bidirectional interlock composite structures showed the highest value of tan delta in weft

direction showing more potential to dissipate energy as compared to the other samples in

both directions, which showed that structure having more value of crimp, would dissipate

more energy. At the same time, bidirectional interlock composites had a balanced or

comparable value of crimp in both directions due to the stacking of both (warp and weft)

structures. While in warp direction, tan delta values of weft and bidirectional interlock

composites were comparable but weft interlock showed more energy dissipation capacity

as compared to the bidirectional interlock composites, which also showed the highest

capacity of energy dissipation in warp and weft directions while warp interlock structure

exhibited the highest potential of energy storage in both directions.

2.4 Conclusions

In this work, three different types of the orthogonal layer to layer interlock composite

structures were produced and their mechanical performance was analysed with four

different characterizations techniques: tensile, impact, flexural strength and dynamic

mechanical analysis (DMA). In tensile behaviour of warp, weft and bidirectional interlock

composites; it can be concluded that warp and weft interlock composites showed the

comparable results of tensile strength, extension at break, and a tensile modulus in warp

61

and weft direction. While in bidirectional interlock composites, tensile strength and

modulus were found to be lesser as compared to the warp and weft interlock composites in

warp and weft directions due to the presence of higher crimp factor in the structure.

Bidirectional interlock composites showed improved impact and three-point bending

performances in warp and weft direction as compared to the other interlocks due to more

compact structure and alternate stacking sequence. DMA results showed that weft interlock

structures in warp direction showed better storage modulus and loss modulus at the same

time in comparison with all other structures. The tan delta values showed that bidirectional

interlock had the highest capacity of energy dissipation both in warp and weft directions.

As an outcome of this research, bidirectional interlock composites are recommended for

transversal direction applications, due to their improved mechanical performance as

compared to the warp and weft interlock composites.

62

Chapter # 3

3D Woven Solid Composite Structures

(Part B)

63

3 Effect of Z-binder yarn on the mechanical performance of hybrid 3D

woven solid composites

In this chapter, an experimental investigation on the effect of Z-binder yarns on mechanical

performance of seven different types of three-dimensional (3D) woven composites i.e.

orthogonal layer to layer (OLL), orthogonal through thickness (OTT), angle interlock layer

to layer (ALL), angle interlock through thickness (ATT), hybrid 1 (H1), hybrid 2 (H2) and

hybrid 3 (H3) is discussed. The jute yarn was used in the 3D woven reinforcements,

whereas green epoxy was used as the resin for composite fabrication. OTT composite

structure showed highest values of tensile stress, modulus and maximum force both in warp

and weft direction as compared to the other 3D interlock structures, due to least

interlacement/crimp of the binder. While ATT composite exhibited highest flexural stress

and flexural modulus both in warp and weft directions due to through thickness angle

binder yarns. Through thickness, interlock composites showed the higher value of force

and interlaminar shear strength (ILSS) for both orthogonal and angle interlock composites

in both warp and weft directions. While H3 had the highest values of force and ILSS in the

warp direction. Whereas, OTT composite showed highest impact strength during Charpy

impact test in both warp and weft directions as compared to the other 3D composite samples

(OLL, ALL, ATT, H1, H2, H3) due to the presence of truly vertical binder yarns. While

hybrid 1 (H1) composite sample displayed comparable impact stress with OTT sample in

both directions. Furthermore, ALL sample exhibited highest maximum force, work done

and energy absorbed during the 3 J and 6 J drop weight impact energies among the four

basic types of 3D woven composites (OLL, OTT, ALL, ATT). Also, hybrid 3 (H3)

exhibited similar drop weight impact test results to ALL sample. With the increase of

impact energy, maximum force, work done and energy absorbed values were also

increased. Hybrid 3 (H3) composite showed the highest value of CAI stress and modulus

in both 3 J and 6 J energy levels due to hybrid warp and weft binder yarns followed by

ATT, OTT, ALL, H1, H2 and OLL composite samples. Also with an increase of impacted

energy, residual stress and modulus values were decreased.

3.1 Introduction

Three dimensional (3D) woven fabric architectures are described by the development of

the binding warp yarns inside the fabric thickness joined with the number of weft yarns and

place of binding warp yarns can be decided by the weave design [1], [24], [25], [153],

[163], [191]. These properties mainly dependent upon the type of fibre, corresponding yarn

and weaving parameters of the reinforcement, type of matrix and of the interface between

them [151], [192]. Depending on the direction of interlacement of Z yarn, 3D woven

64

structures are classified into two major categories: multilayer orthogonal interlock and

multilayer angle interlock [82]. Each of these are further divided into layer to layer (LL)

and through thickness (TT) structures [35], [47], [193] and hybrid woven structures can be

made by combining any of these different 3D structures to get required mechanical

performance depending upon the target applications [9], [41]–[43].

Bilisik and Mohamed [194], [195] developed multi-axis three-dimensional flat woven

preform with tube carrier weaving, tube rapier weaving and circular preform using radial

crossing weaving with five yarn sets as +/– bias, warp, filling and Z-yarns for flat woven

and +/– bias, axial, circumferential and radial yarns for circular woven structures. They

developed a prototype of tube carrier weaving machine for the manufacturing of multi-axis

3D woven preforms. Also, Bilisik [196] developed an innovative forming method of

multiaxial three-dimensional circular woven fabrics while Mohamed et al. [197] developed

a new multilayer three-dimensional fabric producing method.

Huang and Zhong [26] compared the tensile strength and elongation at break of four

different types of 3D woven composites and revealed that to get a dimensionally stable and

mechanically strong composite, the straight arrangement of yarns/filaments would be

preferred and hybrid material would also affect the effective stiffness and strength [40].

While binder yarn volume fraction would not have a significant effect on in plane strength

but increase in binder yarn volume fraction from 3% to 6% would affect the out of plane

properties and increase the delamination resistance of 3D through thickness angle interlock

during flexural test [198]. Similarly, during the shock absorption test of 3D orthogonal

composite on modified shock tube, 6% Z-yarn reinforced composite performance was

better in terms of strength and micro-cracking as compared to the 3% Z-yarn composite

[199].

3D woven interlock composites showed superior impact resistance, knife penetration

resistance, delamination resistance, compressive strength and DMA behaviour as compared

to the unidirectional and laminated counterparts [166], [200], [201]. 3D woven composites

absorbed 25% more impact energy and 12-18% more breaking load as compared to the 2D

woven composites [163]. Also, 3D woven composites showed a higher storage modulus

[164]. Impact energy absorption of 3D woven composites could be several times larger as

compared to the laminated parts showing a higher value of toughness [202]. 3D warp

interlock composites showed higher dynamic elongation during impact keeping the

integrity of woven structure near the impact [23]. During impact, the damage zone remains

localized under the impactor because fibre architecture hinders delamination [203]. Y. Tang

65

et al. revealed energy absorption of 3D angle interlock composites was increased with the

increase of impact velocity with the modified SHPB apparatus [204].

Mahadik and Hallett [117] investigated that the yarn waviness could reduce the in-plane

properties but straighter yarn had a significant effect on the compressive strength of angle

interlock composites and compaction of woven structure in thickness direction had a

significant effect on yarn waviness level in warp and weft. During the flexural test, 3D

orthogonal composite showed significantly higher normalized flexural strength (42%

higher) and moduli (32% higher) as compared to the laminated composites with similar

fibre volume fraction [205]. Flexural performance of the 3D composite was reduced with

the increase of temperature and at room temperature, it showed the highest strength and

modulus [206].

The mechanical performance of 3D woven composites (orthogonal, OI; layer to layer, LL;

angle interlock, AI) under on-axis loading principally depends on the yarn orientation and

fibre volume fraction of warp and weft yarns. While 3D orthogonal woven composites

exhibited the best performance (highest failure strain and failure strength) and highest

energy absorbed under off-axis loading due to the interlocking mechanism of Z-yarn. The

interlocking pattern increased the rotation angle of both warp and weft yarns thus increasing

the ability of yarn to bear off-axis strain [207]. Under impact, no visible delamination was

observed in 3D orthogonal carbon/carbon composites as compared to the laminated

composite which showed prominent delamination and tensile fracture [208]. Also, voids

and microcracks were two major manufacturing defects in composites and with 0.51% void

volume fraction, the tensile strength of the 3D orthogonal composite was reduced to 13.2%

as compared to the intact material [170]. The absence of crimp and minimal waviness in

3D through thickness orthogonal woven structures would be the major advantages in quasi-

static tensile strength [209].

Hallal et al. [210] studied the effect of a number of weft yarns on longitudinal Young's

modulus of multilayer composites and a corrective function was given for the said

estimation. During open hole quasi-static tensile and fatigue tests of 3D orthogonal and

angle interlock composites it was found that, notched tensile strength was 17% lower than

un-notched tensile strength while under 60% of ultimate failure stress no complete fracture

was seen after 5,000,000 cycles and orthogonal interlock composite had larger damaged

surface area as compared to the angle interlock composite [211]. Fatigue fracture and

damage micro-mechanism were analysed by X-ray computed tomography [212] and X-ray

microtomography [213]. Karahan et al. determined the range of maximum cyclic stress of

3D orthogonal carbon/epoxy composite, corresponding to the 3 million cycle life, was

66

between 412 MPa to 450 MPa for both directions. While average fatigue life in warp

direction was three times longer than the weft direction loading [214]. During the 3-point

bending fatigue test of 3D angle interlock composites, it was found that fatigue life was

decreased with the increase of stress level and initial stiffness was decreased gradually with

the increase in testing cycles [215]. 3D orthogonal interlock composite could carry more

elastic bending load but carry a shorter period of fatigue life under the specific stress level

than 3D angle interlock composite [216].

Bilisik et al. revealed that in 3D fully interlaced and semi-interlaced structures, yarn to yarn

spaces were higher as compared to the traditional 3D structures due to the directional

interlacement [217]. Furthermore, with the increase in fibre volume fraction of z-binders,

fracture toughness and fatigue resistance were increased gradually and steep angle caused

the z-binder yarns connecting the delamination cracks and fail in shear and through-

thickness tension [218].

Damage resistance and compression after impact strength mainly depend on the fibre

architecture and were significantly higher in different 3D woven composites as compared

to the unidirectional and laminated composites [115]. The mechanical performance of 3D

woven composites also dependent on the resin rich area and waviness of load carrying fibre,

which was found by the fibre architecture. The interlocking points within the resin rich area

were the damage initiation points in all structures [219] and longitudinal stiffness decreased

non-linearly with the increase in crimp percentage both in 3D fabric [220] and composite

[181].

3D woven composites were also used in different smart applications like; vascular channels

[221] and acoustic emission [222] were used in 3D orthogonal composites to check the in-

plane tensile properties and damage progression in the structure. Similarly, polymer optical

fibers were also embedded in 3D orthogonal composites as in-situ sensors to detect damage

during impact, bending loads [223], [224] and strain measurement [225], while

piezoresistive fibrous sensors [226] were used for mapping of compression and traction at

the top and bottom sides of reinforcement during bending test.

Many researchers worked on the 3D woven composites and compared their mechanical

properties. But, rare work found on the 3D woven hybrid composite structures. In this

study, seven different types of 3D novel woven structures were produced with extra stuffer

yarns and novel hybrid structures and converted into their corresponding composites using

compression moulding plates. The influence of the hybrid z-binder yarns and interlocking

patterns on the in plane and out of plane properties of the fabricated composites was

investigated.

67

3.2 Materials and Methods

3.2.1 3D woven fabric structures

Jute yarn being biodegradable, cheaper and renewable/sustainable was used to develop four

layered 3D woven interlock structures/reinforcements. Also, specific tensile modulus and

tensile strength [227], [228] of jute is comparable with E-glass filament yarn. The linear

density of jute yarn used was 8 lbs/spindle (278 tex or 2500 denier). Yarn tensile tests

(ASTM 2256) were conducted on Uster Tensorapid and average tensile strength of jute

yarn was 99.44 cN/tex.

Seven different types of four layered 3D woven interlock fabric structures (Table 3.1) were

produced on terry loom having dobby mechanism. Threads per centimetre were counted as

per standard ASTM D 3775 for each sample are given in Table 3.1. Shedding mechanism

was controlled by mechanical dobby with take-up control and dual beam loading capacity.

One beam was used for stuffer and low crimp yarns and a second beam for higher crimp

yarns to control the warp breakage during production. Take up control mechanism was used

to stack weft yarns one over the other and finally, a column of weft yarns was achieved.

Table 3.1 Specifications of 3D woven fabrics/reinforcements specifications

Sample

Notation

3D

Nomenclature

Type of 3D woven

multilayer

Ends

/10cm

Picks

/10cm

Aerial

density

(g/m2)

F1 OLL Layer to layer (LL)

Orthogonal interlock (O)

126 319 788±2

F2 OTT Through thickness (TT)

Orthogonal interlock (O)

126 322 794±2

F3 ALL Layer to layer (LL) Angle

interlock (A)

126 315 781±3

F4 ATT Through thickness (TT)

Angle interlock (A)

126 322 795±2

F5

H1

(Hybrid 1)

Combination of Through

thickness (TT) Orthogonal

interlock (O) and Through

thickness (TT) Angle

interlock (A)

stitching/interlocking pattern

126 313 783±2

F6

H2

(Hybrid 2)

Combination of Through

thickness (TT) Orthogonal

interlock (O) and Layer to

layer (LL) Angle interlock

(A) stitching/interlocking

pattern

126 315 781±3

F7

H3

(Hybrid 3)

Bidirectional interlock

(Combination of warp and

weft interlock)

126 322 795±2

68

In first six warp interlock woven structures, extra stuffer yarn was used in warp direction

while in F7, warp interlock was stacked over the weft interlock and weft interlock was

stacked over the warp interlock alternatively. F1, F2, F3 and F4 fabric/reinforcements were

the four basic types of 3D interlock structures i.e. orthogonal layer to layer (OLL) and

orthogonal through the thickness (OTT), layer to layer angle interlock (ALL) and through

thickness angle interlock (ATT) with extra stuffer yarns in the warp direction. While hybrid

1 F5(H1), hybrid 2 F6(H2) and hybrid 3 F7(H3) reinforcements were prepared using the

combination of more than one stitching/interlocking patterns as shown in Table 3.1. Cross

sectional views of F1 to F6 and schematic view of F7 are shown in Figure 3.1.

Figure 3.1 Cross sectional views of F1 to F6 woven fabric structures and schematic view

of F7 woven fabric structure

F7

Warp Interlock Weft Interlock

Weft Interlock Warp Interlock

69

Weave design of orthogonal layer to layer F1(OLL) and orthogonal through thickness

F2(OTT), layer to layer angle interlock F3(ALL) and through thickness angle interlock

F4(ATT), hybrid 1 F5(H1), hybrid 2 F6(H2) and hybrid 3 F7(H3) is given in APPENDIX

3.1, APPENDIX 3.2, APPENDIX 3.3, APPENDIX 3.4, APPENDIX 3.5, APPENDIX 3.6,

APPENDIX 3.7 respectively. After weaving, desizing of all the woven reinforcements was

done with hot water to dissolve polyvinyl alcohol (PVA) from jute yarn to avoid the fibre–

matrix interface problem.


3D woven fabric structures F1, F2, F3, F4, F5, F6, F7 were fabricated to their corresponding

composites using the combination of hand lay-up and compression moulding techniques

and named as their 3D nomenclature i.e. OLL, OTT, ALL, ATT, H1, H2 and H3

respectively for composites. The resin was applied using the vacuum assisted resin transfer

moulding technique and then this uncured composite plate was placed between the

compression plates for 3 hours using 15 bar pressures for complete consolidation and curing

of the composite plate. The fibre volume faction of the produced composite plates was

32%. The thickness of seven different 3D woven composites i.e. OLL, OTT, ALL, ATT,

H1, H2 and H3 was 3.73, 3.45, 3.68, 3.40, 3.76, 3.70 and 3.80 mm respectively. Warp wise

cross-sectional view of 3D woven composite samples were shown in Figure 3.2.

Two-component green epoxy resin CHS-EPOXY G530 was used during composite

manufacturing which was supplied by Spolchemie Pvt. The Ltd Czech Republic and the

same polymer was also used by S. Rwawiire et al. [229]. It was a universal un-modified

liquid low molecular weight epoxy resin based on bisphenol A. As we know that, green

epoxy would degrade after a certain period and finally the composite structure would

deform and would not harm the environment. Now a day, bio resin is preferred in structural

and automotive application [230], [231]. Cycloaliphatic amine (Telalit 0600) was used as

a hardener. Resin and hardener were used with 3:1 ratio. Physical and chemical properties

of green epoxy are shown in Table 3.2.

Table 3.2 Physical and chemical properties of the green epoxy resin

Property Specifications

Density at 20 °C (g/cm³) 1.16

Viscosity 8.0 ~ 10.0 Pas

Glass transition temperature Tg (°C) 72 ~ 75

Gel time (23°C) 51 min

70

Figure 3.2 Warp wise cross-sectional views of 3D woven composites


The mechanical performance of the 3D woven multilayer composites was investigated by

different tests. 3D woven multilayer composites were investigated by tensile properties

(ASTM D3039) having a sample size of 250 mm long and 25 mm wide, flexural properties

(ASTM D7264) having a sample size of 120 mm long and 13 mm wide, short beam shear

test (ASTM D2344) with sample size 30 mm long and 10 mm wide, and compression after

impact (ASTM D7137) having sample size 150 mm long and 100 mm wide using the

universal testing machine (Z100 All-round, Zwick) having capacity 100 KN, whereas

Charpy impact tester (ISO 179) having sample dimensions of 80 mm long and 10 mm wide

was used to check the complete fracture behaviour while for residual fracture energy during

low velocity impact, drop weight impact tester (ASTM D 7136) using sample dimensions

i.e. 150 mm long and 100 mm wide was used. Drop weight impact did not cause the

complete destruction of the specimen and residual energy can be determined. Testing

fixtures of above-mentioned tests are shown in Figure 3.3. Each testing was repeated three

times for every sample and mean of the results were reported. Mean curves were drawn for

each testing parameter as shown in APPENDIX 3.8.

Figure 3.3 Testing fixtures of (a) tensile test (b) flexural test (c) short beam shear test (d)

pendulum impact test (e) drop weight impact test (f) compression after impact test

71

3.3 Results and discussion

3.3.1 Tensile properties

Tensile stress and failure mechanism of 3D warp interlocked composites were checked both

in warp and weft direction to check the effect of binder and stuffer yarns on the composite

structures. Tensile stress versus extension (%) curves of seven different 3D woven

composites in warp and weft directions were shown in Figure 3.4(a) and Figure 3.4(b)

respectively. In weft direction, tensile stress and extension percentage values were higher

as compared to the warp direction due to the more number of yarns in weft direction as

given in Table 3.1. In the initial part of both warp and weft curves, there was slight

horizontal portion reason being little slippage on samples in the jaws. The 1st region of the

curve, up to extension level 0.5% is elastic region and characterized by a linear increase in

the curves. This region represented by the initial response of the material and apparently

damage free zone. At the end of this portion, curve started deviating from linearity. Before

attaining the yield point, the curve showed the elastic region displaying elastic modulus. At

the end of this curve sample reached to the yield point and in this region composite was

softening in a linear manner and failure occurred at 1.2 ~ 2% and 2 ~ 3% extension in warp

and weft direction respectively as shown in Figure 3.4(a) and Figure 3.4(b). Since, yield

point and fracture point of all composite samples were similar, which revealed the brittle

nature of samples.

Figure 3.4 Tensile stress versus extension (%) curves of 3D woven composites (a) warp

wise (b) weft wise

In first six 3D warp interlock composites (OLL, TT, ALL, ATT, H1, H2), binder yarn

passed over and under the weft yarns in the thickness direction to hold the structure. The

undulation, tension of the binder yarn induced some crimp in the structure. While in H3

composite sample binder yarns were in both warp and weft directions, resulting in more

0

5

10

15

20

25

30

35

40

0 0.5 1 1.5 2 2.5 3 3.5

Ten

sil

e s

tress [

MP

a]

Extension [%]

Warp wise (a)

OLL

OTT

ALL

ATT

H1

H2

H3

0

10

20

30

40

50

60

70

80

0 0.5 1 1.5 2 2.5 3 3.5

Te

nsil

e s

tre

ss [

MP

a]

Extension [%]

Weft wise (b)

OLL

OTT

ALL

ATT

H1

H2

H3

72

crimp in warp and weft direction. Therefore, in 3D woven composite structures tensile

stress value was highest in the weft direction and lowest in the warp direction. Since OTT

gave the lowest value of crimp in the warp yarns and revealed the highest value of tensile

stress in the warp direction and in weft direction as well.

In warp direction, tensile stress and extension percentage values were between 22 ~ 30 MPa

and 1.5 ~ 2 % respectively. All samples showed brittle behaviour and broken right after the

yielding point was approached. Tensile stress was more prominent in OTT and ALL

samples after maximum extension level as compared to the other five samples. Tensile

stress value of all 3D composites in warp direction was lower as compared to the weft

direction due to a lesser number of ends and more crimp of yarns both in warp and binder

yarns. When composite was stretched in the warp direction, initially, warp yarns would

tend to straight then elastic region and yielding points would occur. Within the four basic

types (OLL, OTT, ALL, ATT) of 3D woven composites, tensile stress value was highest

of OTT composite sample followed by ALL, OLL and ATT samples. Orthogonal through

thickness interlock weave design had the least interlacement of binder yarns because in this

structure binder yarn passed over the first layer and under the last layer binding all the

layers together instead of binding every layer, resulting in less value of crimp. While within

three hybrid (H1, H2, H3) composite samples, H2 composite sample showed highest tensile

stress which had a combination of orthogonal through thickness and Angle interlock layer

to layer stitching patterns followed by H1 and H3 samples. There was a very minor

difference in tensile stress of H1 and H3 hybrid composites. Furthermore, extension

percentage was highest in ALL composite sample followed by OTT, OLL and ATT in warp

direction because ALL had combined effect of angled more crimped interlocking yarns.

Orthogonal through thickness (OTT) composite samples exhibited a highest value of tensile

stress and second highest value of extension percentage in warp direction as compared to

the all other composite samples.

In weft direction, tensile stress (40~70MPa) and extension percentage (2~3%) values were

higher as compared to the warp direction due to the higher pick density and less crimp in

weft yarns as shown in Figure 3.4(a). Within four basic types of 3D woven composites

(OLL, OTT, ALL, ATT) like in warp direction, weft direction also showed highest value

of tensile stress for OTT composite sample followed by ATT, OLL and ALL samples. Also,

extension percentage was highest in OTT composite sample in weft direction due to the

presence of least crimped interlocking yarns. Whereas, in three hybrid composite samples

(H1, H2, H3), H1 showed the highest value of tensile stress and lowest value of extension

percentage followed by H2 and H3, because H1 had both orthogonal and angle interlock

73

through thickness binding yarns. Through thickness binding yarns had lower crimp as

compared to the layer to layer binding yarns. While in hybrid samples (H1, H2, H3), there

was no significant difference in tensile stress values due to the hybrid binding yarns.

Orthogonal through thickness (OTT) composite samples exhibited the highest value of

tensile stress and extension percentage in weft direction as compared to the all other

composite samples due to the least crimp in the structure.

Table 3.3 Tensile properties of 3D woven composites

Nomenclature

Warp wise Weft wise

Tensile

modulus

(MPa)

Maximum

Load

(N)

Tensile

modulus

(MPa)

Maximum

Load

(N)

OLL 1793±4 2458±7 2277±4 4449±10

OTT 1890±7 2846±9 3610±9 6157±15

ALL 1807±6 2668±8 2929±7 5130±12

ATT 1800±5 2451±4 3556±8 5557±14

H1 1692±4 2590±5 2832±6 5054±11

H2 1870±7 2690±4 2076±3 3492±8

H3 1625±4 2264±3 2512±4 4077±9

Other tensile test properties of seven different composite samples in both warp and weft

directions like tensile modulus and maximum load values are also given in Table 3.3. In

weft direction, tensile modulus and maximum force values were higher as compared to the

warp direction due to less crimp and higher number of yarns in the weft direction. 3D

orthogonal through thickness (OTT) composite showed highest values of tensile modulus

and maximum both in warp and weft directions. In warp direction, OTT composite sample

exhibited the highest value of tensile modulus and maximum force followed by ALL, ATT

and OLL composite samples. However, within three hybrid (H1, H2, H3) composite

samples, H2 composite sample showed highest values of tensile modulus and maximum

force, which had combination of orthogonal through thickness and Angle interlock layer to

layer stitching patterns followed by H1 and H3 samples like tensile stress results as shown

in Figure 3.4(a).

74

Similarly, within four basic types of 3D woven composites (OLL, OTT, ALL, ATT), OTT

composite sample also showed highest values of tensile modulus and maximum force in

weft direction followed by ATT, ALL and OLL samples are given in Table 3.3. This was

due to the more number of weft yarns in the tensile testing clamps and less crimp in weft

direction of the 3D woven structures. Whereas, in three hybrid composite samples (H1, H2,

H3), H1 showed the highest value of tensile modulus and maximum force in weft direction

followed by H3 and H2 composite samples. Overall, 3D orthogonal through thickness

interlock (OTT) composite structure showed highest values of tensile stress, modulus and

maximum force both in warp and weft direction as compared to the other 3D interlock

(OLL, ALL, ATT, H1, H2, H3) composite structures. Due to least interlacement of binder

in the whole structure. Also, within the 3D hybrid samples, H2 showed highest values of

tensile stress, modulus and maximum force in warp direction and H1 showed best results

in weft direction. Tensile strength of 3D woven composite structures was also statistically

significant, because P value was less than 0.05 as highlighted Table 3.4 of ANOVA results.

3D woven structures showed significant effect on tensile strength of composite structures.

Table 3.4 ANOVA for tensile strength of composite structures


Factor 6 14853.2 7426.58 560.35 0.003

Error 10 73.2 12.04

Total 16 12927.4


The three-point bending tests were performed on the 3D woven composites with constant

rate of loading at 5 mm/min and flexural stress versus deformation (%) curves of the OLL,

OTT, ALL, ATT, H1, H2, H3 in warp and weft are shown in Figure 3.5(a) and Figure

3.5(b) respectively. In the elastic region, the stress was increased faster with increasing mid

span deflection. Once the peak stress was reached, there was a sudden drop in the flexural

stress for both weft and warp directions of all 3D composite samples. All the samples

behaviour was brittle except OLL sample in both warp and weft directions which showed

a little strain hardening region on a curve. In weft direction, flexural stress was high as

compared to the weft direction in all composite samples due to higher number of yarns in

weft direction. The flexural stress was found to be highest in case of ATT sample in weft

directions while in warp direction flexural stress of ATT and ALL samples was highest and

comparable. Whereas, deformation percentages of mostly samples in warp direction fall in

3 ~ 3.5% while in weft direction between 2 ~ 3% deformation.

75

Figure 3.5 Flexural stress versus deformation (%) curves of 3D woven composites (a)

warp wise (b) weft wise

In warp direction, flexural stress and deformation percentage values were between 20 ~ 45

MPa and 1.5 ~ 4 % respectively. All samples showed near brittle behaviour and broken

right after the yielding point was approached. Flexural stress was more prominent in ATT

and ALL samples after maximum deformation percentage as compared to the other five

samples. While, OLL composite sample had the least flexural stress in the warp direction.

In a comparison of two orthogonal samples, orthogonal through thickness (OTT) sample

showed more flexural stress as compared to the orthogonal layer to layer (OLL) interlock

composite sample. A similar trend of flexural stress was observed in two angle interlock

composite structures i.e. Through thickness angle interlock (ATT) had comparable value

of flexural stress with the layer to layer angle interlock (ALL). This trend was due to the

vertical binding yarns in through thickness samples. Through thickness vertical binding

yarn would resist more to the transversal force as compared to the layer to layer binding

yarns.

In a comparison of flexural stress of three hybrid samples (H1, H2, H3), H1 composite

samples showed the highest value of flexural stress followed by H3 and H2 sample in warp

direction. Because, in H1 sample contained orthogonal and angle through thickness binder

yarns which would resist more to the transversal direction and its flexural stress was

comparable with ATT as shown in Figure 3.5(a). While H2 composite also had both angle

layer to layer (ALL) and orthogonal through thickness (OTT) interlocking/binder yarns,

that’s why it had more flexural stress than OTT sample and but less than ALL composite

sample as shown in Figure 3.5(a). Furthermore, H3 sample contained binding yarns both

in warp and weft direction and exhibited less flexural stress as compared to the H1

composite sample and more than H2 composite sample.

0

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Weft wise (b) OLL

OTT

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H1

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H3

76

In weft direction, flexural stress and deformation percentage values were between 30 ~ 90

MPa and 2 ~ 4 % respectively. All samples showed brittle behaviour and broken right after

the yielding point was reached except OLL composite sample which showed a little ductile

curve. In the comparison of four basic 3D composite structures (OLL, OTT, ALL, ATT),

Like warp direction as shown in Figure 3.5(a), in weft direction structures having through

thickness binder yarns showed more value of flexural stress as compared to the structures

with layer to layer binder yarn in both orthogonal and angle interlock structures as shown

in Figure 3.5(b). Angle interlock structures would resist more as compared to the

orthogonal interlock structures due to presence of angled binding yarn. Also. through

thickness binder yarns would resist more to flexural force as compared to the layer to layer

binder yarns. Because in orthogonal through thickness structures binding yarns were in the

vertical direction while in through thickness angle interlock binding yarns were passing

through the complete structure at a certain angle. Also, angle interlock through thickness

(ATT) composite sample showed more flexural stress than orthogonal through thickness

(OTT) interlock. Furthermore, in comparison of hybrid interlock composite samples (H1,

H2, H3), H3 composite sample showed the highest value of flexural stress followed by H1

and H2. Also, H3 sample had comparable flexural stress with OTT composite sample. H1

and H2 both showed least similar flexural stress than all other composite samples.

Table 3.5 Flexural modulus of 3D woven composites

Nomenclature

Flexural modulus (GPa)

Warp wise Weft wise

OLL 1.58±0.01 4.09±0.02

OTT 1.73±0.02 5.09±0.03

ALL 1.85±0.01 5.27±0.03

ATT 2.54±0.02 6.85±0.03

H1 2.42±0.02 3.28±0.02

H2 2.20±0.01 2.94±0.01

H3 2.34±0.02 4.17±0.02

Flexural modulus of seven different composite samples in both warp and weft directions

are given in Table 3.5. In weft direction, flexural modulus values were higher as compared

to the warp direction due to less crimp and higher number of yarns in the weft direction. In

warp direction, ATT composite sample exhibited the highest value of tensile modulus

followed by ALL, OTT and OLL composite samples. In hybrid samples (H1, H2, H3), H1

77

showed highest flexural modulus in comparison with other hybrid samples which was

comparable with ATT composite sample in warp direction. Because H1 had both

orthogonal and angle interlock through thickness binding yarns.

Similarly, in weft direction, ATT composite sample showed the highest flexural modulus

as compared to the ALL, OLL, OTT, H1, H2, H3 samples given in Table 3.5. Also, Angle

interlock composite showed better flexural behaviour as compared to the orthogonal

interlock composite samples. While, within the hybrid composite samples in weft direction

H3 sample displayed the highest value of flexural modulus as compared to the H2 and H3.

Overall, 3D angle interlock through thickness (ATT) composite showed highest values of

flexural stress and flexural modulus both in warp and weft directions as compared to the

other 3D composite samples (All, OLL, OTT, H1, H2, H3) due to through thickness binder

yarns. While, within the 3D hybrid composite samples, H1 showed highest flexural stress

and flexural modulus in warp direction and H3 showed best results in the weft direction.

Flexural strength of 3D woven composite structures was also statistically significant,

because P value was less than 0.05 as highlighted Table 3.6 of ANOVA results. 3D woven

structures showed significant effect on flexural strength of corresponding composite

structures.

Table 3.6 ANOVA for flexural strength of composite structures


Factor 2 1653.2 726.58 275.35 0.002

Error 4 19.2 3.04

Total 8 1937.4

3.3.3 Short beam strength (SBS) properties

Short beam strength test is used to determine interlaminar shear strength (ILSS) of parallel

fibres. The interlaminar shear strength is one of the most important parameters to determine

the ability of a composite to resist delamination damage. Three-point-bending (TPB) short

beam strength test was performed to check the localized damage occurred [232]. Although

shear was the dominant applied loading in the method, internal stresses would be complex

and variety of failure modes could occur. The SBS test was performed on the 3D woven

composites with a constant rate of loading at 1mm/min and no delamination, inelastic

deformation or flexural breakage was observed in the samples but only samples showed a

little bend from centre showing interlaminar shear as shown in Figure 3.6. Standard force

versus deformation curves of the OLL, OTT, ALL, ATT, H1, H2, H3 in warp and weft

directions are shown in Figure 3.7(a) and Figure 3.7(b) respectively.

78

. Figure 3.6 Deformation during interlaminar shear test

Figure 3.7 Force versus deformation curves of 3D woven composites (a) warp wise (b)

weft wise

The different behaviour of maximum force against deformation curves was observed in

warp and weft directions. Overall, standard force value was higher in weft direction due to

higher number of yarns in the weft direction and maximum deformation value was

comparable in both directions. At the end of the test, no delamination was found in any

sample 3D woven composites.

In warp direction, within the four basic types of 3D interlock composites (OLL, OTT, ALL,

ATT), through thickness interlock composites showed the higher value of force than the

layer to layer interlock composites for both orthogonal and angle interlock structures.

While, ATT composite structure showed the highest force among the four basic types of

3D woven structures. Because the through thickness binder yarn would resist more in out

of plane direction than the layer to layer binder yarn. Furthermore, among the three different

hybrid composites (H1, H2, H3), H3 composite sample showed the highest force followed

0

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600

0 0.5 1 1.5

Sta

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Warp wise (a) OLL

OTT

ALL

ATT

H1

H2

H3

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Weft wise (b) OLL

OTT

ALL

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H1

H2

H3

79

by the H2 and H1. Among all seven-different 3D woven composite samples, H3 composite

showed highest value of maximum force in warp direction.

While in weft direction, among the four basic types of 3D structure (OLL, OTT, ALL,

ATT), similar trend of increase in force was observed like in warp direction i.e. through

thickness interlock composites showed higher force than the layer to layer interlock

composites for both orthogonal and angle interlock composite structures. But the value of

force was higher in weft direction due to more number of yarn density in weft direction.

This increasing trend of maximum force during short beam shear was similar to the flexural

properties during the flexural testing as shown in Figure 3.5. While within the hybrid

composite samples, H3 composite sample showed the highest value of force followed by

H2 and H1. This increase in force in the weft direction of hybrid samples was similar to the

force increasing in the warp direction of hybrid composite samples.

Furthermore, Interlaminar shear strength of seven different composite samples in both warp

and weft directions are given in Table 3.7.

Table 3.7 Interlaminar shear strength of 3D woven composites

Nomenclature

Interlaminar shear strength (MPa)

Warp wise Weft wise

OLL 4.5±0.2 8.2±0.5

OTT 5.7±0.3 11.5±0.7

ALL 4.7±0.2 5.9±0.3

ATT 5.9±0.3 10.5±0.7

H1 3.3±0.1 6.0±0.3

H2 4.9±0.3 7.2±0.4

H3 8.0±0.5 9.6±0.4

A similar increasing trend of interlaminar shear strength was observed in warp and weft

directions like of standard force values. In warp direction, ATT sample showed higher

value of interlaminar shear strength as compared to the ALL composite sample and

similarly, OTT sample displayed more ILSS value in comparison with ALL sample.

Whereas within the hybrid samples, H3 showed highest value of ILSS followed by H2 and

H1 samples. Similar trend of increase in ILSS value was observed in weft direction, but

ILSS values were higher in weft direction due to more number on picks in weft direction.

Overall, through thickness interlock composite samples showed higher value of standard

force and interlaminar shear strength for both orthogonal and angle interlock composite

80

structures within the four-basic 3D composite structures (OLL, OTT, ALL, ATT) in both

warp and weft directions. While, in hybrid 3D composites samples (H3, H2, H1), H3

showed higher values of force and ILSS both in warp and weft directions. Also, H3

composite sample showed comparable results with other basic 3D woven composites in

weft direction. Interlaminar shear strength of 3D woven composite structures was also

statistically significant, because P value was less than 0.05 as highlighted Table 3.8 of

ANOVA results. 3D woven structures showed significant effect on interlaminar shear

strength of corresponding composite structures.

Table 3.8 ANOVA for interlaminar shear strength of composite structures


Factor 2 1653.2 726.58 275.35 0.002

Error 4 19.2 3.04

Total 8 1937.4

3.3.4 Pendulum impact test results

The impact strength of all 3D woven composite samples were characterized by Charpy

impact tester and their mean values of impact strength in both warp and weft directions are

plotted in Figure 3.8. The key element of attention in impact strength results was the

interlocking pattern, crimp and compactness of the structure. The 3D woven structures

provide an inherent capability to dissipate energy over a larger area than 2D woven systems

with similar fiber volume fraction [66]. Impact strength of all the samples was calculated

by using the dissipated energy and area of the tested samples. This damage tolerance in 3D

woven composites is due to unique energy absorption behaviour, which involve the

crimped portion of through thickness yarns in the 3D composites [182].

Figure 3.8 Pendulum impact strength of 3D woven composites

0

50

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150

200

OLL OTT ALL ATT H1 H2 H3

Imp

act

str

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gth

(k

J/m

2)

Sample ID

Warp wise Weft wise

81

In both warp and weft directions, a similar trend of increase or decrease in impact strength

was observed in all composite samples, but in the weft direction, impact strength value was

higher for all composite samples due to higher pick density. Amongst the four basic types

of 3D woven composites, OTT composite sample showed the highest impact strength

followed by ALL and ATT and least impact strength was showed by OLL sample in both

directions. Because in OTT structure, binder yarns were truly in through thickness direction

joining all the layers together forming the yarn bunch, resulting in higher impact strength.

Least crimp in the binder yarns of OTT structure was also the reason of higher impact

strength. While in ALL and ATT composite structures, a decreasing trend of impact

strength was observed because binder yarns were at a certain angle would bear lower energy

resulting lower impact strength as compared to the truly vertical binder yarn in orthogonal

through thickness (OTT) composite structure.

Furthermore, in hybrid samples (H1, H2, H3), H1 composite sample exhibited higher

impact strength in both directions followed by H3 and H2 samples. H1 sample had the

combination through thickness orthogonal and through thickness angle interlock binder

yarns. That’s why, H1 sample showed higher impact strength as compared to the H2 and

H3 samples. Whereas, H1 impact strength was lower than OTT sample and higher than

ATT sample. H2 sample had a combination of orthogonal through thickness and layer to

layer angle interlock binder yarns, due to the presence of layer to layer angle interlock

binder yarns, H2 showed the least value of impact strength. Also, H3 sample had a

combination of warp and weft interlock structures in both directions and its impact strength

was comparable with H2 and ATT composite samples.

Overall, orthogonal through thickness (OTT) composite sample showed highest impact

strength in both warp and weft directions as compared to the other 3D composite samples

(OLL, ALL, ATT, H1, H2, H3) due to the presence of truly vertical binder yarns. Whereas

within the hybrid samples (H1, H2, H3) H1 composite samples, showed the highest impact

strength in both directions, while nearest to the impact strength of OTT composite sample.

Impact strength of 3D woven composite structures was also statistically significant,

because P value was less than 0.05 as highlighted Table 3.9 of ANOVA results. 3D woven

structures showed significant effect on impact strength of corresponding composite

structures.

Table 3.9 ANOVA for Charpy impact strength of composite structures


Factor 2 1453.2 526.58 290.35 0.001

Error 6 17.2 2.04

Total 8 1637.4

82

3.3.5 Drop weight impact

The drop weight impact is the common method to investigate the impact resistance of

composite materials, in which masses with different energies were dropped on the same set

of specimens fixed on a horizontal plane. The impact event did not cause the complete

destruction of the specimen and helped us to evaluate progressive degradation and damage

tolerance with increasing impact energies. Impact energy could be varied by changing the

mass or height of the impactor. Impact damage and subsequent tolerance of the composite

structure was influenced by the impactor energy and properties of the composite i.e. type

of fiber and matrix, thickness, stiffness, fiber volume fraction and fiber matrix interface.

All the parameters affect the geometry and shape of the damage zone [81].

In this work, a comparison was carried out looking at seven different 3D woven composite

structure (OLL, OTT, ALL, ATT, H1, H2, H3) at two different impact energy levels i.e. 3

J and 6 J using instrumented drop weight impact tester. The variation of impact parameters

such as, force, impact energy, absorbed energy and work done versus time or displacement

were examined to understand the response of 3D woven composites under impact loading.

The force versus displacement curves for seven different 3D woven composites under 3 J

and 6 J impact energies are shown in Figure 3.9(a) Figure 3.9(b) respectively. Whereas,

force versus time curves for 3 J and 6 J impact energies are depicted in Figure 3.10(a) and

Figure 3.10(b) respectively.

83

Figure 3.9 Force versus displacement curves of 3D woven composites (a) at 3 Joule

impact energy (b) at 6 Joule impact energy

Under 3 J impact energy, amongst four basic types of 3D woven composites (OLL, OTT,

ALL, ATT), ALL composite sample showed the highest value of force against maximum

displacement as shown in Figure 3.9(a). Because ALL composite structure contained binder

yarns at a certain angle would resist more to the free fall mass drop. Shorter float of binder

yarns at a certain angle would resist more to the free fall impact mass as compared to the

longer floats at a certain angle and truly orthogonal binder yarns. Therefore, 3D layer to

layer angle interlock (ALL) structure showed the higher value of force against similar

displacement with through thickness angle (ATT) interlock composite. Whereas, 3D

orthogonal layer to layer (OLL) and orthogonal through thickness (OTT) interlock

structures, OTT sample showed higher force against comparable displacement with OLL

sample. Little structural cracks were observed in all 3D composite samples as shown in

Figure 3.13.

Furthermore, in three different types of hybrid composites (H1, H2, H3), H3 sample

exhibited a higher value of force against maximum displacement followed by H1 and H2.

H3 composite sample had lesser binder yarn floats due to stacking warp and weft interlock

one over the other alternatively. While H1 and H2 both had orthogonal binder yarns with

least interlacement showing least values of force against maximum displacement. Also, H3

composite sample gave almost bell-shaped curve dropping off at the zero level of force

84

with 2 mm permanent deformation. H3 composite samples showed comparable maximum

force and maximum displacement values with the angle layer to layer interlock composite

(ALL) sample.

A similar trend of increase in maximum force against displacement was observed in 6 J

impact energy for all 3D woven composite samples (OLL, OTT, ALL, ATT, H1, H2, H3)

like in 3 J impact energy tests as shown in Figure 3.9(b). But, maximum force and

displacement values were higher as compared to the 3 J impact energy values. Amongst the

four basic types of 3D woven composites, 3D layer to layer angle interlock (ALL)

composite sample showed the highest force against maximum displacement followed by

ATT, OTT, OLL. While within the three hybrid composite samples, H3 sample showed the

highest value of force against displacement followed by H1 and H2. But, ALL and H3

composite samples showed little bell-shaped curve not approaching to zero force value.

Maximum displacement values were highest in OLL, H2 and H1 sample followed by other

3D composite samples.

Force and displacement in all samples increased with the increase of impact energy [233],

would also be further explained by force versus time curves of 3D woven composite

samples under 3 J and 6 J impact energy as shown in Figure 3.10(a) and Figure 3.10(b). A

similar trend of increase in force versus time was observed in all 3D woven composite

samples under 3 J and 6 J impact energies. With the increase of time, force values were

increasing at both impact energy levels.

85

Figure 3.10 Force versus time curves of 3D woven composites (a) at 3 Joule impact

energy (b) at 6 Joule impact energy

In 3 J impact energy test, testing time was about 5 milliseconds except for H3 samples

while in 6 J impact energy test, testing time was about 15 milliseconds and force values

were up to 900 N. Within the basic 3D woven composite types, ALL showed the highest

value of force with the increasing time followed by ATT, OTT and OLL at both impact

energy levels. Whereas, amongst the three hybrid samples, H3 composite sample showed

the highest value of force with increasing test time followed by H1 and H2 during both

energy levels. In 3 J test, only H3 composite sample force value was approached to zero

while during the 6 J test, H3 and ALL composite samples force values to move downward

after peak value but not approaches to zero. ALL composite sample showed the highest

value of maximum force against time likewise of force versus displacement curves, also

comparable with H3 composite sample at both impact energies i.e. 3 J and 6 J.

Maximum work done during both impact energy levels i.e. 3 J and 6 J for all 3D composite

samples is highlighted in Figure 3.11(a) and Figure 3.11(b) respectively. Also, energy

absorbed versus test time at both impact energy levels is depicted in Figure 3.12(a) and

Figure 3.12(b). Amount of work done was increased with the increase of impact energy.

The increasing or decreasing trend of work done during the drop weight impact test was

similar to the maximum force. So, maximum force bear by each 3D composite sample also

justified with the amount of work done during 3 J and 6 J impact energy tests.

86

Figure 3.11 Work done versus time curves of 3D woven composites (a) at 3 Joule impact

energy (b) at 6 Joule impact energy

Work done versus test time, in 3D woven composites (OLL, OTT, ALL, ATT, H1, H2,

H3), was highest in H3 sample nearest followed by layer to layer angle interlock (ALL)

composite then ATT, OLL, H1, OLL and H2 composites samples during 3J impact energy

test. Only H3 sample showed a little bell-shaped curve during the 3 J impact energy test,

while in 6 J impact energy test, the amount of work done was increased but, H3 and ALL

both showed near bell-shaped in the work done curves, which was the similar behaviour

observed in force versus time and force versus displacement curves at 6 J impact energy.

0

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0 2 4 6 8

Work

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0 5 10 15

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87

Figure 3.12 Energy absorbed (a) at 3 Joule impact energy (b) at 6 Joule impact energy by

3D woven composites

During impact, energy is absorbed in the form of matrix cracks, delamination initiation,

propagation and fibre fracture. Energy absorbed during the drop weight impact test was

increased with the increase of impact energy as shown in Figure 3.12(a) and Figure 3.12(b).

ALL showed highest amount of energy absorbed adjacent followed by H3 samples during

both 3 J and 6 J impact energies. All other 3D composite samples (ATT, OLL, OTT, H1,

H2) showed the comparable value of absorbed energies during both levels of impact

energies.

Overall, layer to layer angle interlock composite (ALL) showed the highest amount of

maximum force versus displacement and time, work done and energy absorbed during the

3 J and 6 J drop weight impact energies among the four basic types of 3D woven composites

(OLL, OTT, ALL, ATT). While within the three hybrid (H1, H2, H3) composite samples,

H3 exhibited the highest amount of maximum force, work done and energy absorbed and

comparable results with ALL composite sample.

Damage assessment

Visual assessment of physical damage apparent in the material showed that damage

increased with the increase in impact energy. The face of the specimens exhibited the

evidence of damage and crack was observed in the composite surfaces. Damage was more

concentrated at the point of impact but a line of crack was observed in the samples. Some

of the samples with damage zones during 3 J impact and 6 J impact energies were shown

in Figure 3.13(a) and Figure 3.13(b) respectively which showed that damage zone and its

severity was increased with the increase of impact energy. The binder yarns act as a crack

arrestor, suppressing delamination by reducing the crack driving force. During an impact

event, binder yarn interlacement would create more hindrance to crack propagation and

delamination damage. So, the matrix crack/delamination damage would be arrested at the

1.0

1.5

2.0

2.5

3.0

3.5

H3 H2 H1 ATT ALL OTT OLL

Absorbed

en

erg

y [

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Sample ID

(a)

3

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Absorbed

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Sample ID

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88

point of each binder intersection and causes less interfacial damage. Furthermore, the

damage width and propagation depends on the distance between two binder yarns as well

as the position and number of the binder yarns per unit area under and around the impactor.

More binders situated around the impacted area means a restriction of damage propagation.

Since all the three samples were warp interlocked, so all the samples were characterized in

the warp direction. During the warp-impacted test, the damage propagates more in the warp

direction due to the longer floats of warp yarn, and the damage shape becomes elliptical

with an increase in impact energy. A similar phenomenon was observed by King [234] for

3D woven orthogonal composites. The through-thickness/binder yarn minimized the

development of delamination damage and subsequent propagation by enhancing

interlaminar fracture toughness.

Figure 3.13 Damage zones during (a) 3 Joule impact energy and (b) 6 Joule impact

energy tests

3.3.6 Compression after impact (CAI) properties

The term “damage tolerance‟ is typically associated with the residual stress of the target

material following impact. In-plane compression is believed to be the critical loading mode

89

for impact-damaged specimens, as the stress reduction is largest under this type of loading.

Therefore, a widely accepted characteristic of damage tolerance is obtained using the

compression-after-impact (CAI) test. This characteristic is called compression after impact

(CAI) stress or residual compressive stress [115], [234]. Compression after low velocity

impact properties of 3D multilayer composites was higher as compared to the 2D laminated

composite structures. While, in 3D multilayer composite structures, density, type and

direction of stitching/interlocking were found important structural parameters. CAI load on

multilayer composites showed larger damage area near the impacted region but

delamination confined to the relatively smaller area [235], [236]. The residual compressive

stress values versus deformation percentage for the 3D woven structures after 3 J and 6 J

impact energy test was plotted in Figure 3.14(a) and Figure 3.14(b) respectively.

Figure 3.14 CAI stress versus deformation (%) curves of 3D woven composites after (a)

3 Joule impact energy (b) 6 Joule impact energy

Compression after impact (CAI) stress was decreased with the increase of impact energy.

H3 hybrid composite exhibited highest residual stress at both energy levels followed by

ATT, OTT, ALL, H1, H2 and least CAI stress depicted by OLL composite sample. Because

in OLL composite sample, damaged area and width of the impacted sample was higher

after drop weight impact testing as compared to the other 3D composite samples. On the

other hand, H3 and ATT samples had least damaged area during the impact testing. The

drop weight impact testing damages greatly affect the residual stress. Also, in H3 sample

warp and weft interlock structures were stacked one over the other alternatively. After H3

samples, through thickness interlock structures showed better resistance to the compression

jaws. That’s why ATT and OTT composite structures showed better CAI stress after H3

samples. Whereas, both layer to layer interlock structures i.e. OLL, ALL showed least CAI

stress due to the presence of binder yarn in one direction. Structure with the layer to layer

binder yarns in both directions showed higher residual stress as highlighted by H3

0

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0 2 4 6

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ALL

ATT

H1

H2

H3

0

5

10

15

20

25

0 2 4 6

Str

ess

[MP

a]

Deformtion [% ]

(b)

OLL

OTT

ALL

ATT

H1

H2

H3

90

composite sample. While H1 and H2 showed the intermediate value of CAI stress and H1

sample had more CAI stress as compared to the H2 because H1 had both orthogonal

through the thickness and through thickness angle binder yarns. But CAI stress of H1

sample was lower than individual orthogonal through the thickness and through thickness

angle interlock composites. Which showed a combination of interlocking pattern in one

direction was not fruitful to get higher residual stress.

Table 3.10 CAI modulus of 3D woven composites

Sample ID

CAI modulus (MPa)

After 3 Joule impact energy After 6 Joule impact energy

OLL 378±4 351±4

OTT 496±5 449±5

ALL 428±5 396±4

ATT 635±6 606±7

H1 420±4 381±4

H2 397±3 365±3

H3 703±7 625±5

Furthermore, residual compressive modulus values for 3D woven composite structures

after 3 J and 6 J impact energy test are given in Table 3.10. The 3D composite sample

showed a similar trend of increasing or decreasing the CAI modulus as of CAI stress. H3

composite showed the highest value of CAI modulus followed by ATT, OTT, ALL, H1,

H2 and least CAI modulus showed by OLL composite sample at both energy levels.

Overall, H3 composite sample showed the highest value of CAI stress and modulus after

drop weight impact test at both 3 J and 6 J energy levels due to hybrid warp and weft binder

yarns followed by ATT, OTT, ALL, H1, H2 and OLL composite samples. Also with an

increase of impacted energy residual stress and modulus values were decreased.

3.4 Conclusions

In this study seven different types of 3D woven composites i.e. orthogonal layer to layer

(OLL), orthogonal through thickness (OTT), layer to layer angle interlock (ALL), through

thickness angle interlock (ATT) and three different hybrid interlock composites H1

(combination of OTT and ATT binder yarns), H2 (combination of OTT and ALL binder

yarns), H3 (combination of warp and weft interlock) were fabricated using compression

moulding technique. Six different types of characterizations (tensile, flexural, interlaminar

91

shear, Charpy impact, drop weight impact, CAI) were done to check their mechanical

performance and followings conclusions were made.

1. 3D orthogonal through thickness interlock (OTT) composite structure showed

highest values of breaking tensile stress, modulus and maximum force both in warp

and weft direction as compared to the other 3D interlock (OLL, ALL, ATT, H1,

H2, H3) composite structures. Because of the least interlacement of binder in the

whole structure. Also, within the 3D hybrid samples, H2 showed the highest values

of tensile stress, modulus and maximum force in the warp direction and H1 showed

best results in the weft direction.

2. 3D angle interlock through thickness (ATT) composite showed highest values of

flexural stress and modulus both in warp and weft directions as compared to the

other 3D composite samples (All, OLL, OTT, H1, H2, H3) due to through thickness

binder yarns at a certain angle. While, within the 3D hybrid composite samples, H1

showed highest flexural stress and flexural modulus in the warp direction and H3

showed the best results in the weft direction.

3. 3D through thickness interlock composite samples showed the higher value of

standard force and interlaminar shear strength for both orthogonal and angle

interlock composite structures within the four-basic 3D composite structures (OLL,

OTT, ALL, ATT) in both warp and weft directions. While, in hybrid 3D composites

samples (H3, H2, H1), H3 showed higher values of force and ILSS both in warp

and weft directions. Also, H3 composite sample showed comparable results with

other basic 3D woven composites.

4. Orthogonal through thickness (OTT) composite sample showed highest impact

strength during Charpy impact test in both warp and weft directions as compared to

the other 3D composite samples (OLL, ALL, ATT, H1, H2, H3) due to the presence

of truly vertical binder yarns. Whereas within the hybrid samples (H1, H2, H3) H1

composite samples, showed the highest impact strength in both directions, while

nearest to the impact strength of OTT composite sample.

5. Layer to layer angle interlock composite (ALL) showed the highest amount of

maximum force versus displacement and time, work done and energy absorbed

during the 3 J and 6 J drop weight impact energies among the four basic types of

3D woven composites (OLL, OTT, ALL, ATT). While within the three hybrid (H1,

H2, H3) composite samples, H3 exhibited the highest amount of maximum force,

work done and energy absorbed and comparable results with ALL composite

92

sample. Work done and energy absorbed during the tests were increased with the

increase of impact energy.

6. Hybrid H3 composite sample showed the highest value of CAI stress and modulus

after drop weight impact test at both 3 J and 6 J energy levels due to hybrid warp

and weft binder yarns followed by ATT, OTT, ALL, H1, H2 and OLL composite

samples. Also with an increase of impacted energy residual strength and modulus

values were decreased.

Overall, during in plane testing (tensile), OTT composites sample behaved

mechanically well due to the least crimp in binder yarn, while during out of plane

characterizations (flexural, ILSS, low velocity impact and CAI), both through thickness

structures (OTT and ATT) and hybrid 3 (H3) sample showed highest and comparable

mechanical results.

93

Chapter # 4

3D Woven Spacer Composite Structures

(Part C)

94

4 Effect of pile height on compression/recovery properties of 3D woven

spacer fabric reinforced composites

In this chapter, different mechanical and time dependent properties of the 3D woven spacer

fabrics composites are explained. In literature, time dependent compression & recovery

behaviour of 3D woven spacer fabric composites is not studied. In this work, the results on

needle penetration, flexural, low velocity impact and dynamic compression & recovery

properties of 3D woven spacer composites having three different thickness levels (4 mm,

10 mm and 20 mm) are reported. 3D woven spacer E glass/epoxy composites were

fabricated using spray and hand lay-up method. Bending length of 3D woven spacer fabric

was decreased and stiffness was increased with the increase in pile height and fabric

thickness. While in 3D woven spacer fabric composites, 20 mm (Comp20) thick composite

was more penetration resistant as compared to the 10 mm (Comp10) and 4 mm (Comp4)

thick composites. Flexural, low velocity impact and flat compression performance of the

3D woven spacer fabric composites were reduced with the increase of sample thickness.

Besides, the Highest amount of energy was absorbed during fracture of 4 mm (Comp4)

thick sample followed by 10 mm (Comp10) and 20 mm (Comp20) thick composites.

Compressibility (%) and resiliency (%) was highest in 4 mm thick composite but recovery

(%) was a bit lower as compared to the 10 mm and 20 mm thick composites. While in 10

mm thick composite recovery percentage was highest. Furthermore, 4 mm thick composite

showed highest values of work done during cyclic compression loading-unloading testing,

showing more toughness followed by 10 mm and 20 mm thick composites.

4.1 Introduction

Three-dimensional (3D) spacer woven fabric is developed by interconnecting two or more

layers together with vertical pile yarns. The 3D spacer fabric composites can offer high

skin-core deboning and impact resistance, excellent durability and superior integrity, high

stiffness, excellent thermal insulation, acoustic and damping. The application prospects of

these products are in an automobile, locomotives, aerospace, marine, windmills, building

and other industries [44]. These structures are ideal for the applications, where weight is an

important consideration. The reduction in weight gives many advantages such as higher

speed, larger payloads, less consumption of engine power and better working economy

[237].

Conventional spacer structures are made of core material having low density and facesheets

of high modulus such as honeycomb and foam. These are joined together with an adhesive

to produce the lightweight panels [238]. The surface area available for bonding at the

face/core interface is very limited for this kind of structures, which can cause the

95

delamination at the bonding interface. Due to this reason, it has turned into the primary area

of concern with the traditional spacer structures under external impacts [239]. There is an

extreme reduction in compressive strength due to core damage and delamination in case of

low and intermediate velocity impacts such as tool drops, hailstorms, runway debris and

high strain rate impacts which can be by projectile damage or crash conditions [106], [240].

To overcome the shortcomings in the conventional spacer structures, few alternative

methods are used for manufacturing the progressive spacer structures, primarily including

stitching [237] and Z-pinning [241], [242]. The stitching and pinning system of the

structures filled by foam was effective in improving the through the thickness properties,

particularly the impact damage tolerance. However, both approaches would certainly

decrease the in-plane properties due to the translaminar reinforcement [243]. Furthermore,

these structures are very tough to be stitched or pinned. Nowadays, several new 3D fabric

structures have become popular, because of their cost-benefit, good mechanical

performance and design diversity [62], [193].

Different researchers have assessed the mono-spacer fabric composite panels with respect

to its drum-peel strength, flatwise compressive strength and transversal shear modulus [62],

[138], [139]. They revealed that a very significant skin-core debonding resistance exists in

the fabric reinforced composites. It has also been investigated that the pile yarns played a

vital role on the flatwise compression and shear properties. 3D hollow structures and 3D

integrated laminates with foam filled core were analysed by Hosur et al. [140], [141] under

low-velocity impact response. Li. et al. [44] investigated the mechanical performance of

corrugated and 8-shape piles spacer structure and revealed that corrugated piles showed

much better anisotropic behaviour as compared to the 8-shaped pile structure. Furthermore,

the mono-spacer fabric composites failed under flat compressive load due to the broken or

slanted piles, and the performance would be optimized at pile angle of 80°–90°. Whereas

piles cracked at its endpoints under shear load, while during edgewise compression test

mono-spacer fabric composite failed by the facesheet wrinkling.

Flat compression properties were decreased with the increase of core heights and the flat

load-displacement curves exhibited obvious elastic, plasticity plateau and densification

stage while the warp compression properties increased with the increase of core heights

and only the elastic stage was obvious for the flat load-displacement curves. Moreover, the

flat compression properties were superior to the warp compression in the value [142].

Besides, shear resistance is anisotropic for the corrugated core. When it is sheared in the

warp direction, one-half of the walls are extended and the other is compressed, which

results into a ductile failure mode with a relatively low shear strength and stiffness [244].

96

Bending experiment of 3D spacer composite with 4 mm thick facesheet showed that the

thick facesheets could enhance the bending load resistance capacity significantly [143].

Energy absorbed decreased and damage of the composite increased with the increase of

core heights (5 mm,10 mm, 15 mm, 20 mm, 25 mm, 30 mm) [45]. Bending stiffness, three-

point bending and four-point bending load, increased with the increase of thickness (8 mm,

10 mm, 12 mm) of E-glass/vinyl ester 3D woven spacer composite both in the warp and

weft direction but in warp direction stiffness and load values were higher. During a three-

point bending failure of a thicker panel was dominated by the crippling and shear failure

within the skins [144].

Quasi-static compression of glass/ethoxylene 3D spacer composite showed tilting of fibre

piles initially which lead to the simultaneous deformation of the cores by compression and

shear. After the elastic buckling of the curved piles, there is a plastic rotation of the piles

which enables the deformation with a long stable plateau [144]. The epoxy panels of 3D

woven glass fabric with polyurethane foam showed excellent fatigue behaviour, very long

lifetime and low stiffness degradation as compared to those without polyurethane foam

[245]. Mountasir et al. developed GF/PP hybrid spacer composite structure and revealed

that the mechanical properties of the composites (tensile strength, flexural stiffness, and

compression properties) were enhanced by a reduction in yarn damage in the non-crimped

layers of the woven fabric structures [246]–[248]. Additionally, the flexural stiffness,

edgewise compressive strength and specific flatwise compressive strength of the integral

multi facesheets 3D woven spacer composites were higher as compared to the mono-spacer

fabric composites and bonded multi-facesheet [249]. Ashir et al. also produced the spacer

fabric with steel wires and carbon rovings [250].

Furthermore, numerical methods were also used to investigate compression behaviour of

3D spacer fabrics [251]. Also, finite element results were in good agreement with the

experimental results of flat compression, shear, three and four point bending, edgewise

compression, for 3D woven spacer [252], syntactic-foam/glass fiber [253] composites and

core properties [138] (compression and shear) of pile and foam filled composites.

The process of moderating the design comprises different considerations, including, the

shape of the structure, which affects load transmission during impact, and the capacity to

absorb elastic energy, which controls rebound [254]. 3D Spacer fabric structures due to

their excellent compression strength, durability, insulation, recyclability, pressure

distribution, energy absorption capacity, fire retardancy and anti-bacterial properties are

used in multiple high performance areas e.g. cycle helmets, firemen helmets, body armours,

boot soles, marble reinforcements, boat structures, surfboards, train body parts and

97

baseplate, tanks, wound care dressing, orthopaedic support bandages, compression therapy

goods, and different parts of car body parts such as; body panels, door panels, trunk, wheel

covers, headliners, dashboards.

Although some research has been carried out in the past on mechanical characterization of

3D woven spacer fabric composites. But the dependence of mechanical properties on the

thickness and dynamic compression/recovery behaviour of 3D woven spacer composites

has not been reported in the literature. The aim of the present work was to investigate

flexural, penetration, impact, compression & recovery properties and energy absorption

during compression & recovery of 3D woven spacer fabric composites. The damage and

fracture morphology of the composites was observed using a microscope and the failure

mechanism is reported. Furthermore, the influence of composite thickness (with different

pile yarn height and pile direction) on mechanical properties is also discussed.

4.2 Materials and Methods

4.2.1 3D woven spacer fabric

3D woven spacer fabric/reinforcements comprising E-glass (264 tex) fibre were obtained

from Qinhuangdao Taidao Trade Co., Ltd. China. the configuration of the 3D woven spacer

fabric is shown in Figure 4.1. These fabrics comprised of two woven facesheets, connected

together with vertical pile yarns. Depending upon the direction of the yarns, three different

types were used in the structure, including straight warp and weft individually in the Z and

Figure 4.1 Yarn placement of 3D woven spacer fabric/reinforcement

Y directions of top and bottom facesheets, and the pile yarns in Z direction producing S

shape. 8-shaped pile in the X direction (warp direction) was formed by combining two S-

shaped pile yarns and the I-shaped pile was formed in the Y direction (weft direction). The

pile yarns in the facesheets are in the warp direction, along which fabric was rolled up.

Spacer fabrics can be designed with many variations, with pile height, warp yarns density,

98

weft yarns density, the distribution density of piles. 3D woven spacer fabrics used in this

study had three different thickness levels i.e. 4 mm, 10 mm and 20 mm and were named

Fab4, Fab10 and Fab20 respectively. Detailed specifications of 3D woven spacer fabric are

given in Table 4.1.

Table 4.1 Specifications of 3D woven spacer fabrics

3D woven spacer

Item fabric

Fab4

Fab10

Fab20

Areal density

(g/m2)

Top layer 325 ± 04 325 ± 04 325 ± 04

Pile 160 ± 03 730 ± 06 1360 ± 10

Bottom layer 325 ± 05 325 ± 04 325 ± 06

Total 810 ± 6 1380 ± 8 2010 ± 10

Thickness (mm) 4.0 10.0 20.0


3D woven spacer composites having three thickness levels (4 mm, 10 mm and 20 mm)

were fabricated by hand lay-up technique and named as Comp4, Comp10 and Comp20

respectively. Two-component green epoxy resin CHS-EPOXY G530 was used during

composite manufacturing which was supplied by Spolchemie Pvt. The Ltd Czech Republic

and the same resin was also used by Rwawiire et al. [229]. It was a universal un-modified

liquid low molecular weight epoxy resin based on bisphenol A. Green epoxy would degrade

after a certain period and finally, the composite structure would deform and would create

less hazardous waste. Now a day, bio-resins are preferred in structural and automotive

application [230], [231]. Cycloaliphatic amine (Telalit 0600) was used as a hardener. Resin

and hardener were used with a 3:1. Physical and chemical properties of green epoxy are

given in Table 4.2.

Table 4.2 Physical and chemical properties of the green epoxy resin

Property Specifications

Density at 20 °C (g/cm³) 1.16

Viscosity 8.0 ~ 10.0 Pas

Glass transition temperature Tg (°C) 72 ~ 75

Gel time (23°C) 51 min

99

A flat aluminium mould was used in the process and the releasing agent was coated on its

surface. Initially, 40% of the total resin was applied uniformly using a spray gun on flat

mould, and then the spacer fabric was positioned over it having warp direction parallel to

Figure 4.2 Cross sectional view of 3D woven spacer fabric composites: (a) warp direction

(b) weft direction

the length of the mould. The ends of the fabric in weft direction were fixed with aluminium

mould. The resin was allowed to impregnate from the bottom facesheet, and the remaining

60% of the resin was sprayed over the top facesheet. The fibre volume fraction of the

produced composite plates was 39±0.6% calculated by Equation 1.1. Cross sectional views

of composite samples both in warp and weft directions are shown in Figure 4.2(a) and

Figure 4.2(b) respectively.


The mechanical performance of the 3D woven spacer fabric (Fab) and their corresponding

3D woven spacer composites (Comp) was investigated by different tests. 3D woven spacer

fabrics were characterized by checking stiffness using circular bend procedure (ASTM D

4032-94) and bending length on cantilever apparatus (ASTM D 1388).

While 3D woven spacer fabric composites were investigated by: slow penetration (puncture

test, EN 388) at speed of 5 mm/min on universal testing machine (Lloyd) having 5KN

capacity with sample size of 125 mm long and 75 mm wide, flexural properties (ASTM

D7264) of sample size 120 mm long and 13 mm wide, flat compression (ASTM C365) of

sample size 75 mm long and 75 mm wide, low velocity impact properties (ASTM D 7136)

using 8.338 kilograms mass and 3.28 m/s impact velocity on drop weight impact tester

having sample size of 150 mm long and 100 mm wide, single cycle compression and

recovery test (ASTM F36) and cyclic compression and recovery test using the universal

100

testing machine (Z100 All-round, Zwick) having capacity 100 KN. Each testing was

repeated three times for every sample and an average of the results were reported.

4.3 Results and Discussion

4.4 3D woven spacer fabric

Bending length and stiffness of 3D woven spacer fabrics having three different thickness

(4 mm, 10 mm, 20 mm) are shown in Table 4.3. Bending length of Fab4 sample was higher

as compared to Fab10 and Fab20. Because, in Fab4 sample, the areal density (GSM) and

pile height were lower as compared to the Fab10 and Fab20 samples as given in Table 4.1.

As the pile height and GSM of the fabric is increased, the fabric would bend at a shorter

length. When the pile height is increased, the weight of the pile would also increase due to

the consumption of more length of glass yarn in pile formation, resulting in an increase in

GSM and decrease in bending length of the fabric.

Table 4.3 Physical testing results of the 3D woven spacer fabric

Sample Notation

Bending length (cm)

(ASTM D 1388)

Stiffness (N)

(ASTM D 4032-94)

Fab4 7.50 ± 0.05 30.50 ± 1.25

Fab10 6.75 ±0.08 84.50 ± 1.75

Fab20 4.25 ± 0.06 102.85 ± 2.50

Similarly, Fab20 fabric sample was stiffer followed by the Fab10 and Fab4 samples. Higher

stiffness value of Fab20 would be related with GSM of the fabric. Higher the GSM of the

fabric, more would be the force (N) required for stiffness as given in Table 4.3.

4.5 3D woven spacer fabric composites

4.5.1 Needle penetration resistance

In needle penetration resistance test, 5mm/min speed was used to check the penetration

resistance of composite samples like spacer fabric reinforcements. The setup for needle

penetration resistance test and load versus extension curves of the Comp4, Comp10 and

Comp20 are shown in Figure 4.3(a) and Figure 4.3(b). The load versus extension results in

showed that there is a significant difference in load required to penetrate in different

samples. This was due to the different pile height and different fabric specifications in three

different sample thicknesses. The 20 mm thick composite sample supported the highest

value of load and extension as shown in Figure 4.3(b).

101

Figure 4.3 (a) Setup of needle penetration test (b) Load versus penetration curves of 3D

woven spacer fabric composites

The load presented two peak points in load versus curves because needle had to pass

through two cured facesheets of composites. 1st peak of the load was due to the resistance

offered by the top facesheet and 2nd peak load was due to the resistance offered by the

bottom facesheet while in centre portion load value was lower. This was due to least

hindrance offered by pile area for needle penetration. Additionally, in top facesheets needle

passed through the composite samples facing less value of load as compared to the bottom

facesheet due to the extra resistance offered by bottom facesheet and piles together. In pile

area, the extension value was highest in Comp20 sample, because in this region needle

offered very low resistance for long time followed by the Comp10 and Comp4 as shown in

Figure 4.3(b).

With the increase in sample thickness, maximum load bearing values of composite samples

were increased, because of the higher stiffness values of their corresponding fabrics as

shown in Table 4.3. Comp20 sample showed the highest values of load and extension

followed by the Comp10 and Comp4. Since similar fibre volume fraction and the same type

of resin was used in composite manufacturing, therefore, this increasing trend in load could

also be explained based on corresponding spacer fabric specifications. Comp20 comprised

fabric with the highest GSM, thus needle would face more resistance in displacing the

yarns. On the other hand, higher GSM fabric will result in a higher value of the load. While

Comp4 had lower GSM in its corresponding fabric showing the lowest value of the

maximum load. In Comp10 and Comp20, yarn linear densities were comparable in both

0

50

100

150

200

250

300

0 10 20 30 40

Load

(N)

Penetration (mm)

3D woven spacer fabric composites (b)

Comp4

Comp10

Comp20

102

warp and weft directions, resulting in little difference of load-bearing capacities. Comp4

sample


The three-point bending tests were performed on the 3D woven spacer fabric composites

with a constant rate of loading at 5mm/min and flexural stress versus deformation (%)

curves of the Comp4, Comp10 and Comp20 in warp and weft are shown in Figure 4.4(a)

and Figure 4.4(b) respectively. The flexural testing setup and fracture behaviour of the

sample are shown in Figure 4.5(a) and Figure 4.5(b) respectively. In the elastic region, the

stress was increased faster with increasing mid-span deflection. Once the peak stress was

reached, there was a sudden drop in the flexural stress for both the weft and the warp

directions of Comp4 and Comp10. Whereas, flexural stress was found to be low in the case

of Comp20 in both directions.

Figure 4.4 Flexural stress versus deformation (%) curves of composites: (a) Warp wise

(b) Weft wise

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35 40 45

Fle

xura

l st

ress

[MP

a]

Deformation [% ]

(a)

Warp wise

Comp4

Comp10

Comp20

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35 40 45

Fle

xu

ral

str

ess [M

Pa]

Deformation [% ]

(b)

Weft wiseComp4

Comp10

Comp20

103

The facesheet failure was observed due to the fracture during bending of the structure as

shown in Figure 4.5(b). In addition, the flexural stress in the weft direction was higher than

that of the warp direction, because fluctuation of the warp and pile yarns in the facesheets

led to a stress loss in the warp direction [44]. I-shaped piles covered more area in weft

direction as compared to the 8-shaped piles in the warp direction and 8-shaped piles

contained more free space causing less force in warp direction as shown in Figure 4.5(b).

Under the maximum force, a shear failure of the piles is occurred [249].

Figure 4.5 (a) Experimental setup of flexural testing of composites (b) Fracture

morphologies

While within the warp direction of three composite samples, flexural stress was decreased

from 4 mm (Comp4) to 10 mm (Comp10) and very low flexural stress was seen in 20 mm

(Comp20) thick composite sample, because of extra length of pile portion in the Comp20

and higher deformation percentage as shown in Figure 4.4(a). Deformation percentage was

also increased with the increase of sample thickness and was the highest in Comp20 sample.

A similar trend of flexural stress and deformation percentage behaviour was found in the

weft direction as shown in Figure 4.4(b).

Furthermore, in all samples double peaks of flexural stress could be observed in both warp

and weft directions, while in Comp20 sample flexural stress was very low, that’s why peaks

were not prominent. The reason behind the double peak was the two facesheets of woven

spacer structure. The 1st peak value of flexural stress was due to the resistance of top

facesheet formerly sudden drop of flexural stress was due to the breakage of top facesheet

and the 2nd shorter peak of flexural stress was due to confrontation of the bottom facesheet

and finally, flexural stress dropped to its minimum value. Peak flexural stress values were

higher in weft direction in comparison with warp direction due to the presence of I-shaped

104

piles which cover more area in the weft direction and offered more resistance to the applied

load. 2nd peaks were more prominent in the warp direction, because 8-shaped piles were

formed in this direction which resists more in the form of a bunch before transferring the

load to the bottom facesheet as compared to the I-shaped piles in weft direction as shown

in Figure 4.5(b).

Flexural modulus results are given in Table 4.4. Flexural modulus values decreased with

the increase of fabric thickness from 4 mm to 20 mm thick sample. The flexural modulus

of Comp20 sample was lowest in both directions.

Table 4.4 Flexural modulus of 3D woven spacer fabric composites

Sample

Notation

Flexural modulus (MPa)

Weft wise Warp wise

Comp4 3456±12 1761±8

Comp10 960±6 238±4

Comp20 20±3 10±2

The flexural modulus of composite samples was found to be higher in weft direction as

compared to the warp direction as given in Table 4.4. The reason behind the higher flexural

modulus in weft direction was same as of flexural stress i.e. 8-shaped piles contained more

free space causing less flexural stress and modulus in the warp direction. The flexural

modulus of Comp20 sample was lowest in both warp and weft direction in comparison with

Comp10 and Comp4 samples, because of extra-long piles height in 20 mm thick sample.

4.5.3 Flat compression properties

For flatwise compression test, the specimens with an area of 76 mm x 76 mm were put on

the circular bearing blocks one by one. Experimental setup and compressive stress-

deformation (%) curves for 3D woven spacer fabric composites with three different

thickness levels, under flatwise compressive loads, are shown in Figure 4.6(a) and Figure

4.6(b) respectively. The behaviour of the composites under flat compression test was

ductile although the composites were made of E glass which has brittle nature. Because of

the glass filaments in the fabric which could only bear load when they are flattened and are

under tension at the same time. Therefore, glass in the piles bear small bending moments;

and the resin surrounding the glass piles played the major role during flatwise compression.

That’s why it can be said that the mechanical performance of 3D woven composite was

improved by increasing the resin ratio at a certain level [255].

105

Figure 4.6 (a) Compressive testing setup (b) Compressive stress versus deformation (%)

curves of 3D woven spacer fabric composites

Flat compression results showed that flat compression properties varied with the core

height. Compressive stress was decreased from 4 mm (Comp4) to 20 mm (Comp20) thick

composite samples and very low compressive stress was found in 20 mm (Comp20) thick

composite sample. Curves showed a linear elastic behaviour until stress peak was achieved.

As the stress peak was reached, the sound of piles cracking could be heard, and the cracks

were firstly detected at the joining point of piles with top and bottom facesheets, slanting

of piles and then finally fracture was occurred. Piles in 4 mm thick sample were first

tilted/slanted from the vertical position until the fracture was observed at its joining point

with the facesheets, while piles in 10 mm thick sample and above were deformed, tilted

and buckled that causes material failure, as shown in Figure 4.7(a)(b)(c), similar results

were discussed by Min Li et al. [44].

Figure 4.7 Fracture morphologies of (a) Comp4, (b) Comp10 and (c) Comp20

0

0.5

1

1.5

2

2.5

3

3.5

4

0 20 40 60

Com

pressiv

e

str

ess [M

Pa]

Deformation [% ]

(b)

Comp4

Comp10

Comp20

106

It can be observed that the core height was an important factor in the compressive

performance. The compressive stress of Comp4 sample was highest because of the very

short length of pile (4 mm) which bear full load before fracture at the facesheet joints with

very little slanting followed by Comp10 (10 mm) and very low in Comp20 (20 mm) sample.

In Comp20 piles could not resist the applied load very long time and slanted and fractured

from the centre part of piles under slight applied compressive load due to the extra-long

length of the pile. Flat compression strength of 3D woven spacer composite structures was

also statistically significant, because P value was less than 0.05 as highlighted in Table 4.5

of ANOVA results. 3D woven spacer structures showed significant effect on flat

compression strength of corresponding composite structures.

Table 4.5 ANOVA for flat compression strength of composite structures


Factor 2 14.213 7.108 15.35 0.003

Error 6 2.2740 0.429

Total 8 16.987

From Table 4.6, it can be observed that maximum compressive force was decreased to

53.96% from 4 mm to 10 mm thick composite while in 20 mm thick composite maximum

force was decreased to 94.7% in comparison with 4 mm thick composite sample. Similarly,

compressive modulus was decreased to 53.09% from 4 mm to 10 mm thick composite while

the compressive modulus value was decreased to 77.43% in comparison with 4 mm thick

composite. Similar results were discussed by the C.Q. Zhao [142].

Table 4.6 Flat compressive testing results of 3D woven spacer fabric composites

Sample

Notation

Maximum

Force (Pmax)

(N)

Compressive

Modulus (Ez)

(MPa)

Compressometer

Deflection (δpmax)

(mm)

Comp4 19400±88 4.5±0.5 1.4±0.2

Comp10 8930±35 2.1±0.2 2.8±0.4

Comp20 1020±15 1.1±0.1 5.7±0.7

The reason behind maximum compressive force and modulus was same of compressive

stress i.e. shorter pile height would bear more load and stiffer as compared to the longer

one. Furthermore, compressometer deflection was increased with the increasing thickness

107

of composites. An indirect relation was found predicted between pile height and

compressive stress values with these composite samples.

Energy absorption during compression

Fracture behaviour of three composite samples could be further analysed based on energy

absorbed during the deformation procedure as shown in Figure 4.8(a)(b)(c). Energy

absorbed (toughness) during fracture was highest in Comp4 followed by Comp10 and

Comp20. Comp4 sample could bear the highest applied load with little deformation as

compared to the other two sample. As encircled in Figure 4.7(a), comp4 sample was first

slanted towards weft and fracture started at the point of contact between piles and facesheets

which absorb more energy during fracture due to the short pile height. Whereas, Comp20

sample showed the lowest value of energy absorbed and highest deformation during the

fracture depicting moderately ductile behaviour in comparison with the other two samples

as shown in Figure 4.8(c). It was obvious that fracture propagation was very fast with the

little plastic region in Comp20 sample. Ductile materials are preferred in most of the

mechanical applications because they exhibit more plastic region and higher energy

absorption before fracture which are intrinsically more safer than brittle materials

presenting more toughness [256]. Furthermore, it can be observed that the energy absorbed

was decreased significantly with the increase in the spacer fabric thickness.

Figure 4.8 Energy absorbed versus deformation curves of (a) Comp4, (b) Comp10 and

(c) Comp20

4.5.4 Low velocity impact

For low velocity impact test, after initial trials on different energy levels, 45 Joule energy

was finalized for testing of all samples on drop weight impact tester. Experimental test

setup and maximum force, puncture deformation and energy absorbed during impact test

of 3D woven spacer fabric composites with three different thickness levels, fracture

morphologies from top side and cross section wise, are shown in Figure 4.9(a), Figure

4.9(b), Figure 4.9(c) and Figure 4.9(d) respectively. It could be found that all the impact

108

test results were sensitive to the pile/core height of composites, and maximum force and

energy absorbed was increased with the decrease of pile/core height. Comp4 displayed the

highest impact force and absorbed maximum energy with the lowest deformation during

puncture in comparison with the other two composites.

Figure 4.9 (a) Experimental setup, (b) results of drop weight impact test and fracture

morphologies (c) on top side (d) cross section wise

Comp4 Comp10 Comp20

0

500

1000

1500

2000

2500

Maxim

um

Forc

e (

N)

Maximumm Force (N)

Puncture Deformation (mm)

Energy Absorbed (J)

Sample ID

(b)

0

5

10

15

20

25

30

35

40

45

50

Punctu

re D

efo

rmati

on (

mm

)

0

5

10

15

20

25

30

35

40

45

50

Energ

y A

bso

rbed (

J)

109

The puncture was visible on the upper and lower side of all the samples and in Comp4

sample longitudinal crack was also found in the surrounding area of puncture. In warp

direction, the 8-shaped column was pressed down and in the weft direction, I-shaped piles

were slanted towards weft as shown in Figure 4.9(d).

Maximum impact force and energy absorbed during puncture were highest in Comp4

sample due to the minimum pile height in comparison with Comp10 and Comp20 samples.

Since the areal density of top and bottom facesheet in all samples was similar but in pile

region, areal density was increased with the increase of pile height i.e. 160, 730, 1360 grams

per square meter of Comp4, Comp10 and Compo20 samples respectively. Therefore, pile

height in the central portion was the significant factor affecting the impact force and energy

absorbed. The impact test results trend was similar to the flat compression test as explained

in Figure 4.6(b) and Figure 4.8(a) i.e. Comp4 sample exhibited highest maximum force and

energy absorbed during the test followed by Comp10 and Comp20 samples. The shorter

length of fibre would be stiffer as compared to the longer one. Puncture deformation was

highest in Comp20 sample as shown in Figure 4.9(b) due to more thickness of sample

followed by Comp10 and Comp4 samples.

4.5.5 Single cycle compression and recovery

For compression and recovery test, the specimens with an area of 76 mm x 76 mm were

put on circular bearing blocks. Compression and recovery cycle was applied in three steps;

in step 1, 20% of maximum compression force as shown in Table 4.6 for 30 seconds, in

step 2, 60% of maximum compression force for 60 seconds and in step 3, 20% of maximum

compression force for 30 seconds were applied on the composite samples. A single cycle

of this load series was applied as shown in Figure 4.10.

Figure 4.10 Single cycle compression and recovery test setup

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Com

pressiv

e

force (

%)

Time (Seconds)

Single cycle compression and recovery test

Step 1

Step 2

Step 3

110

Different compression and recovery test results: thickness under pre-load, thickness under

total load and recovered thickness, compressibility %, recovery % and resiliency % are

shown in Table 4.7. Experimental force versus tool separation curves for 3D woven spacer

composites with three different thickness levels are shown in Figure 4.11(a)(b)(c). Initially,

80% of the total compressive force was applied in the 2nd step, but composites did not

recover their thickness. After that, 60% of the compressive load was decided to be applied

to apply in 2nd step for all composite samples, while in 1st and 3rd steps, 20% of the

compressive force was maintained.

Figure 4.11 Force versus sample thickness curves of (a) Comp4, (b) Comp10 and (c)

Comp20

Comp20 sample was deformed easily under very little compressive load due to extra-long

pile height during compression and recovery cycle, while Comp4 sample showed the

highest resistance against applied cyclic load during deformation as shown in Figure 4.11.

Whereas, in Comp10 sample change in thickness was under a moderate level of applied

force due to moderate pile height (10 mm).

0

5000

10000

15000

3 4 5 6

Force [

N]

Sample thickness [mm]

(a)

Comp4

0

1000

2000

3000

4000

5000

6000

9 9.5 10 10.5

Force [

N]


(b)

Comp10

0

200

400

600

800

16 17 18

Force [

N]


(c)

Comp20

111

Pre-load value of thickness showed that there was no significant difference found in the

thickness value while a significant difference in thickness was found under 60% force for

60 seconds’ time as given in Table 4.7. Recovered values of thickness showed that none of

the three samples was returned to its initial stage after the application of compression and

recovery cycle. There was a permanent or plastic deformation in all composite samples due

to this compression and recovery cycle. The difference in the thickness of Comp4 sample

was most significant after this test followed by Comp10 and Comp20 samples. In the 1st

cycle of 20% force, there was a minor difference in thickness occurred in the composite

samples while in 2nd cycle of 60% force, permanent deformation occurred in the all

samples.

Table 4.7 Compression and recovery test results of 3D woven spacer fabric composites

Sample

Notation

Thickness

under

preload,

(P)

Thickness

under total

load,

(M)

Recovered

thickness,

(R)

Compressibility,

%

(c)

=

[(P-M)/P]

*100

Recovery,

%

(r)

=

[(R-M) /(P-

M)] * 100

Resiliency,

%

(f)

=

[(R-M)/M]

* 100

(mm) (mm) (mm) (%) (%) (%)

Comp4 4.78±0.1 4.44±0.1 4.63±0.1 6.98±0.4 54.61±3 4.10±0.2

Comp10 9.70±0.2 9.42±0.2 9.61±0.2 2.81±0.2 75.32±5 1.95±0.1

Comp20 17.01±0.3 16.41±0.2 16.87±0.3 3.51±0.3 67.33±8 2.74±0.2

Compressibility and resiliency percentages were highest in Comp4 sample but recovery

percentage was lower in comparison with Comp10 and Comp20 samples. In lower pile

height, the compressibility of composite samples was easier but recovery of the sample to

its initial position was difficult. Recovery percentage was highest in Comp10 sample but

lowest in Comp4. In Comp20 recovery percentage values were on the optimum level. Also,

in 4 mm thick sample compressibility percentage was higher in comparison with 10 mm

and 20 mm thick samples. Ability of the Comp4 to spring back (resiliency) into initial

position was highest due to shorter pile height while lowest in Comp10, as in 20 mm thick

samples piles were permanently deformed and damaged from the centre part while in

Comp10 piles were tilted and deformed instead of damage as shown in Figure 4.7(b).

4.5.6 Cyclic compression and recovery

For cyclic compression loading and recovery test, the specimen with an area of 76 mm x

76 mm was put on between the compression testing blocks. Cyclic compression loading

and recovery cycle was applied in two steps; in the 1st step, 60% of total compression force

112

as shown in Table 4.6 for 15 minutes and in 2nd step 10 N force for 15 minutes for recovery

were applied on the composite samples. Five cycles of this load series were applied to each

composite sample. In 1st step 11640 N, 5358 N and 612 N force for the compressive step

of Comp4, Comp10 and Comp20 samples respectively and 10 N force for recovery step

(2nd step) were kept constant for each sample. Since the force was kept constant for each

cycle, thus change in thickness (strain) with time were drawn in Figure 4.12(a)(b)(c) for

each sample. Permanent deformation or change in thickness with time under constant force

was significant in Comp4 and Comp20 samples while a little change in thickness of

Comp10 was found for the 2nd step as shown in Figure 4.12(b). The results of a cyclic test

could be quite complex, due to the creep, stress-relaxation and permanent deformations.

Figure 4.12 Strain versus time curves of (a) Comp4, (b) Comp10 and (c) Comp20 during

compression and recovery test

Due to the application of cyclic load, deformation behaviour was significant in Comp20

and Comp4 while in Comp10 sample deformation was less with the passage of time. When

force was applied on the composites, sliding of structural chains was occurred with the

passage of time, which showed the viscoelastic changes in the composites. With the

application of force all the samples showed instantaneous deformation and in every next

113

cycle, the value of strain was increased with the passage of time which was significant in

Comp20 and Comp4 samples. This increase in strain with time (at the same temperature)

called creep. Significant creep was observed in Comp20 and Comp4 while less creep

behaviour was observed in Comp10 as shown in Figure 4.12(a)(b)(c). After the 1st cycle

creep was significant showing permanent deformation in Comp20 and Comp4 samples

whereas in next four cycles creep was less whereas, in comp10 sample creep was minimum

in 1st step of loading portion. After instant recovery relaxation was increased with every

next cycle in all the samples and samples tried to regain their original position but due to

the damage of piles, could not succeed fully.

After the removal of the load at the end of 5th loading cyclic some creep was observed in

relaxation portion of all samples which was significant in Comp4 followed by Comp20 and

less in Comp10. It could be explained with the crash behaviour of samples as shown in

Figure 4.7. In Comp4 sample piles were fractured at the joining point of facesheets and

sliding of the top and bottom facesheets was observed. Once the piles were fractured, the

strain was observed in the sample, resulting in the increase in deformation. Similarly, in

Comp20 piles were tilted and buckled at the centre portion and deformation occurred

showing the higher value of strain. While in Comp10 tilting of piles and facesheets sliding

was observed under compression loading and very less deformation in piles area was found,

indicating less deformation in structure with the passage of time and less viscoelasticity.

Furthermore, Hysteresis loops for 5 cycles loading-unloading of composite samples were

obtained by plotting the force against strain value which are shown in Figure 4.13(a)(b)(c).

Hysteresis in the samples during compressive cycles could result from changes in the

orientation of individual piles during loading-unloading cycles. When samples in the blocks

were compressed, the vertically aligned individual piles became tilted and less oriented,

requiring the sample to absorb energy. In contrast, on the release of loading, samples try to

recover their orientation while dissipating energy. This energy transfer generated two

distinct loading paths, forming a hysteresis loop [257]. Since all samples showed a time-

dependent elastic behaviour. Therefore, the force versus strain curves were not the same

for loading and unloading. Samples exhibited viscoelasticity, involving both elastic and

viscous components. Energy absorbed during one loading-unloading cycle was given by

the area within the loop. A similar trend of strain change with force was observed in

hysteresis loops as explained in Figure 12. Comp20 sample showed higher creep due to

higher permanent deformation against a constant force with time followed by Comp4 which

was comparable with Comp20 and very less permanent deformation was found in Comp10

sample as highlighted in Figure 4.13(a), Figure 4.13(b) and Figure 4.13(c).

114

Figure 4.13 Hysteresis loop of (a) Comp4, (b) Comp10 and (c) Comp20 during

compression and recovery test

Time dependent behaviour of composite samples could be explained based on work done

during load application, load removal and difference of work done in both regions which

are shown in Figure 4.14(a), Figure 4.14(b) and Figure 4.14(c) respectively.

115

Figure 4.14 Graphs of work done during each cycle (a) force loading, (b) force

unloading and (c) work difference between both

Work done during loading and unloading was highest in Comp4 sample and both values

showed the decreasing trend in all samples. In Comp20, work done values during loading

and unloading cycles were lowest as shown in Figure 4.14(a) and Figure 4.14(b). Because

in loading cycle Comp20 sample bears very less load and slanted and fractured away while

in unloading cycle due to this fracture piles could not retrieve its original position and

deformation occurred. The difference in work done was found to be highest in Comp4 and

showed the decreasing trend, displaying the highest value of strain with the passage of time

depicting more toughness. Higher the value of the difference in work done more would be

the viscoelasticity because less work would be done during load removal portion and value

of strain increased with time. Similarly, in Comp10 and Comp20 samples difference in

work done showed the decreasing trend and lowest in Comp20 sample as shown in Figure

4.14(c). That’s why highest toughness was observed in Comp4. While in Comp10 sample

difference in work done, was between both other samples presenting intermediate

toughness.

116

4.6 Conclusions

In this work 3D woven spacer fabric reinforced composites with three different thickness

levels (4 mm, 10 mm and 20 mm) were produced. Increase in pile length and thickness of

3D spacer fabric reinforcement results in following changes in the mechanical properties

of 3D woven spacer fabric composite structure.

1. Bending length of 3D woven spacer fabrics was decreased, while stiffness was

increased with the increase of sample thickness due to higher areal density (GSM)

and more pile height.

2. While in 3D woven spacer fabric composites, 20 mm thick (Comp20) composite

was more needle penetration resistant due to coarser pile yarn and higher aerial

density followed by 10 mm (Comp10) and 4 mm (Comp4) thick composites.

3. The flexural, low velocity impact and flat compression performance were reduced

with the increase of sample thickness from 4 mm (Comp4) to 20 mm (Comp20)

while flexural stress curves gave two peaks in all samples both in warp and weft

direction due to the top and bottom facesheets. Whereas, flexural behaviour was

better in weft direction as compared to the warp direction. Because I-shaped piles

covered more area in weft direction as compared to the 8-shaped piles in the warp

direction and in 8-shaped piles contained more free space causing less force in the

warp direction. 4 mm thick composite (Comp4) sample showed the highest value

of energy absorbed and lowest deformation during the fracture depicting the

viscoelastic behaviour.

4. Furthermore, compressibility and resiliency percentages were highest in 4 mm

(Comp4) thick composite but recovery percentage was lower in comparison with

10 mm (Comp10) and 20 mm (Comp20) thick composites. Comp10 showed

intermediate compressibility (%), resiliency (%) and highest recovery (%) during

single cycle compression and recovery test. Moreover, a higher value of permanent

deformation with time was exhibited in Comp20 showing higher creep followed by

Comp4 and Comp10 during cyclic compression loading-unloading test. The

difference in work done was also highest during the cyclic test was also highest in

Comp4 sample showing higher toughness in comparison with the other two

samples.

117

Chapter # 5

General Conclusions and Future Perspective

118

5 General conclusions and future perspective

5.1 General conclusions

In this work, two different types of three-dimensional (3D) woven reinforcements i.e. 3D

woven solid and 3D woven spacer structures and their corresponding composites were

investigated under different static and dynamic mechanical loadings. In 3D woven solid

reinforcements i.e. warp, weft, bidirectional and novel hybrid interlock structures were

developed on rapier dobby looms and effect of interlocking pattern and z-binder yarns on

the in plane and out of plane mechanical properties of their corresponding composites was

explained. It was found that the increase in crimp of the binder yarns resulted in the

decrease of in plane mechanical properties compared with the lower crimped binder yarn

3D woven composite structures. Improved in plane and out of plane properties of 3D woven

composites in a specific direction can be achieved by modifying the interlocking pattern

and z-binder yarns. Also, 3D woven spacer fabric reinforced composites with three

different thickness levels (4 mm, 10 mm and 20 mm) were investigated under static and

time dependent loadings. This study was divided into three stages and different conclusions

were made in each stage;

In the first stage, 3D orthogonal layer to layer warp, weft and novel bidirectional

interlock woven composite structures were developed and response of interlocking

pattern on different static and time dependent mechanical loadings was investigated.

Under different mechanical loads the following conclusions were made;

1. The interlocking pattern had a significant effect on the mechanical properties of the

3D woven composite structures.

2. Individual 3D warp and weft interlock composites showed better tensile behaviour

as compared to bidirectional interlock composite in warp and weft directions, due

to the presence of less crimp as compared to 3D bidirectional interlock.

3. 3D bidirectional interlock composite exhibited considerably superior impact

resistance and three-point bending strength as compared to the individual 3D warp

and weft interlock composites.

4. Tan delta values of dynamic mechanical analysis (DMA) results showed that

bidirectional interlock displayed the highest capacity of energy dissipation in warp

and weft directions.

Combined comparative results of 3D novel woven reinforced composites are given in Table

5.1.

119

Table 5.1 Combined comparative results of 3D composites (Stage 1)

Type of 3D

composite

Tensile

properties

Impact

properties

Flexural

properties

DMA

results

Warp Interlock

Composite

✓✓✓✓

✓✓✓

✓✓✓

✓✓

Weft Interlock

Composite

✓✓✓✓

✓✓✓

✓✓

✓✓✓

Bidirectional

Interlock

Composite

✓✓✓

✓✓✓✓

✓✓✓✓

✓✓✓✓

In the second stage, the effect of z-binder yarns on different 3D woven composite

structures during in plane and out of plane mechanical loadings was investigated. Seven

different types of 3D woven structures i.e.orthogonal layer to layer (OLL), orthogonal

through thickness (OTT), angle interlock layer to layer (ALL), angle interlock through

thickness (ATT), and three different novel 3D woven hybrid structures i.e. H1

(combination of OTT and ATT, called H1), H2 (combination of OTT and ALL, called

H2) and H3 (bidirectional) interlocks were developed. In first six 3D woven structures

extra stuffer yarn was used in the warp direction. Under different mechanical tests

following findings were made:

1. Overall, the z-binder yarn had a significant effect on the in plane and out of plane

mechanical properties of the 3D woven composite structures.

2. During in plane testing (tensile), OTT composites sample behaved mechanically

better due to the least crimp in binder yarn,

3. During out of plane characterizations (flexural, ILSS, low velocity impact and

CAI), both through thickness structures (OTT and ATT) and bidirectional (H3)

sample showed highest and comparable mechanical results.

Combined comparative results of 3D novel woven reinforced composites are given in Table

5.2.

120

Table 5.2 Combined comparative results of 3D composites (Stage 2)

Sr.

#

3D

Type

Tensile

properties

Flexural

properties

Short beam

strength

Charpy

impact

Drop weight

impact

Compression

after impact

1 OLL ✓✓✓ ✓✓✓ ✓✓✓ ✓✓ ✓✓✓ ✓✓

2 OTT ✓✓✓✓ ✓✓✓ ✓✓✓✓ ✓✓✓✓ ✓✓✓ ✓✓✓

3 ALL ✓✓✓ ✓✓✓ ✓✓ ✓✓✓ ✓✓✓✓ ✓✓✓

4 ATT ✓✓✓ ✓✓✓✓ ✓✓✓✓ ✓✓✓ ✓✓✓ ✓✓✓✓

5 H1 ✓✓✓ ✓✓ ✓✓✓ ✓✓✓✓ ✓✓✓ ✓✓✓

6 H2 ✓✓ ✓✓ ✓✓✓ ✓✓✓ ✓✓✓ ✓✓✓

7 H3 ✓✓✓ ✓✓✓ ✓✓✓✓ ✓✓✓ ✓✓✓✓ ✓✓✓✓

In the third stage, the effect of pile height on static and time dependent mechanical

loadings of 3D woven spacer composite structures were investigated. 3D woven spacer

fabric composites with three different thicknesses i.e. 4 mm (Comp4), 10 mm

(Comp10) and 20 mm (Comp20) were characterized. Different mechanical loadings

and time dependent compression and recovery properties were investigated and the

following conclusions were made;

1. Pile height had a significant effect on the static and time dependent mechanical

properties of the 3D woven spacer fabric composite structures.

2. Bending length of 3D woven spacer fabrics was decreased, while the stiffness of

the 3D spacer fabric samples was increased with the increase of sample thickness

due to more pile height and higher aerial density.

3. Flexural, low velocity impact and flat compression performance of the 3D woven

spacer fabric composites were reduced with the increase of sample thickness. The

highest amount of energy was absorbed during fracture of 4 mm (Comp4) thick

sample followed by 10 mm (Comp10) and 20 mm (Comp20) thick composites.

4. Compressibility (%) and resiliency (%) was highest in 4 mm thick composite but

recovery (%) was a bit lower as compared to the 10 mm and 20 mm thick

composites. While in 10 mm thick composite recovery percentage was highest. 4

121

mm thick composite showed highest values of work done during cyclic compression

loading-unloading testing.

Combined comparative results of 3D woven spacer composites of this stage are given in

Table 5.3.

Table 5.3 Combined comparative results of 3D spacer composites (Stage 3)

Sample

Notation

Needle

penetration

resistance

Flexural

Properties

Flat

compression

Drop

weight

impact

Single cycle

compression

/recovery

Multi cycle

compression

/recovery

Comp4 ✓✓ ✓✓✓✓ ✓✓✓✓ ✓✓✓✓ ✓✓✓ ✓✓✓

Comp10 ✓✓✓ ✓✓✓ ✓✓✓ ✓✓✓ ✓✓✓✓ ✓✓✓✓

Comp20 ✓✓✓✓ ✓✓ ✓✓ ✓✓ ✓✓ ✓✓

122

5.2 Future Perspective

Recommendations that would be valuable extensions to the development of these materials

include:

1. Numerical modelling all of 3D woven composites using COMSOL or ANSYS

software and comparison with the experimental results.

2. A parallel comparison of different 3D woven structures orthogonal layer to layer

(OLL), orthogonal through thickness (OTT), angle interlock layer to layer (ALL),

angle interlock through thickness (ATT)] with warp and weft binder would help to

fully identify the influence of binder yarn direction on mechanical properties in both

warp and weft directions.

3. Fatigue tests could provide a significant amount of information about the influence

of binder path modification on durability and stability of 3D woven composites with

individual warp and weft binder yarns. Compression and recovery behaviour of 3D

woven spacer composites could be checked up to 1 million cycles.

4. Ageing of 3D woven composites with moisture, temperature and time.

5. Along with short beam shear test, mode-II tests can also be done.

6. 3D spacer structures can be used for sound absorption applications.

7. Real-time testing of 3D woven composite structures for inner and outer body parts

of lightweight vehicles, bullet proof panels and furniture parts will be done.

123

6 References

[1] A. Miravete, 3-D textile reinforcements in composite materials. Cambridge:

Woodhead Publishing Limited, 2000.

[2] L. Tong, P. Mouritz, and K. Bannister, 3D fibre reinforced polymer composites.

Elsevier Ltd, 2002.

[3] F. Walter and M. Hardcastle, Textiles in automotive engineering, Vol. 13.

Woodhead Publishing, 2001.

[4] B. Griffiths, “Boeing sets pace for composites usage in large civil aircraft,” 2005.

[5] M. K. Bannister, “Development and application of advanced textile composites,”

Proc. Inst. Mech. Eng. Part L J. Mater. Des. Appl., vol. 218, no. 3, pp. 253–260,

2004.

[6] R. Kamiya, B. A. Cheeseman, P. Popper, and T. W. Chou, “Some recent advances

in the fabrication and design of three-dimensional textile preforms: A review,”

Compos. Sci. Technol., vol. 60, no. 1, pp. 33–47, 2000.

[7] A. Bibo, G.A., Hogg, P.J., Backhouse, R. and Mills, “Carbon-fibre non-crimp

fabric laminates for cost-effective damage-tolerant structures,” Compos. Sci.

Technol., vol. 58, no. 1, pp. 129–143, 1998.

[8] J. Brandt, K. Drechsler, and F. Arendts, “Approaches for improving the damage

tolerance of composite structures,” in Developments in the Science and Technology

of Composite Materials, 1990, pp. 509–516.

[9] A. P. Mouritz, M. K. Bannister, P. J. Falzon, and K. H. Leong, “Review of

applications for advanced three-dimensional fibre textile composites,” Compos.

Part A Appl. Sci. Manuf., vol. 30, no. 12, pp. 1445–1461, 1999.

[10] B. N. Cox, M. S. Dadkhah, W. L. Morris, and J. G. Flintoff, “Failure mechanisms

of 3D woven composites in tension, compression, and bending,” Acta Metall.

Mater., vol. 42, no. 12, pp. 3967–3984, 1994.

[11] Ko and K. Frank, Three-dimensional fabrics for composites. Elsevier Science

Publishers Limited, 1989.

[12] F. Chen and J. M. Hodgkinson, “Impact behaviour of composites with different

fibre architecture,” Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng., vol. 223, no. 7,

pp. 1009–1017, 2009.

[13] R. B. Mohamed, M.H., Bogdanovich, A.E., Dickinson, L.C., Singletary, J.N. and

Lienhart, “A new generation of 3D woven fabric preform and composites,” Sampe

J., vol. 37, no. 3, pp. 8–17, 2001.

[14] R. Mark and A. Robinson, “Principles of weaving.” Manchester, U.K: The Textile

124

institute, 1976.

[15] J. Soden and B. Hill, “Conventional weaving of shaped preforms for engineering

composites,” Compos. Part A Appl. Sci. Manuf., vol. 29, no. 7, pp. 757–762, Jul.

1998.

[16] C. S. Smith, Design of marine structures in composite materials. England: Elsevier

Science Publishers Limited, 1990.

[17] M. Niu, “Composite Airframe Structures,” Hong Kong Conmilit Press Ltd, 1992.

[18] R. I. Haresceugh, “Aircraft and aerospace applications of composites,” in

Pergamon Press plc., Concise Encyclopedia of Composite Materials, 1989, pp. 1–

7.

[19] P. Beardmore, “Automotive components: fabrication,” in Pergamon Press plc,

Concise Encyclopedia of Composite Materials, 1989, pp. 24–31.

[20] D. H. Bowen, “Applications of composites: an overview,” in ergamon Press plc,

Concise Encyclopedia of Composite Materials, 1989, pp. 7–15.

[21] P. M. Wambua and R. Anandjiwala, “A Review of Preforms for the Composites

Industry,” J. Text. Inst., vol. 40, no. 10, pp. 310–333, 2010.

[22] S. Nauman and I. Cristian, “Geometrical modelling of orthogonal/layer-to-layer

woven interlock carbon reinforcement,” J. Text. Inst., vol. 106, no. 7, pp. 725–735,

2015.

[23] F. Boussu, M. Lefebvre, D. Coutellier, and D. Vallee, “Experimental and high

velocity impact studies on hybrid armor using metallic and 3D textile composites,”

in CAMX-The Composites and Advanced Materials Expo, 2014.

[24] F. Boussu, I. Cristian, and S. Nauman, “General definition of 3D warp interlock

fabric architecture,” Compos. Part B Eng., vol. 81, pp. 171–188, 2015.

[25] D. Sun and X. Chen, Three-dimensional textiles for protective clothing. 2015.

[26] H. Gu and Z. Zhili, “Tensile behavior of 3D woven composites by using different

fabric structures,” Mater. Des., vol. 23, no. 7, pp. 671–674, 2002.

[27] Y. Z. Wan, G. Zak, S. Naumann, S. Redekop, I. Slywynska, and Y. Jiang, “Study

of 2.5-D glass-fabric-reinforced light-curable resin composites for orthotic

applications,” Compos. Sci. Technol., vol. 67, no. 13, pp. 2739–2746, 2007.

[28] J. Jekabsons and J. Varna, “Micromechanics of damage accumulation in a 2.5D

woven C-fibber/SiC ceramic composite,” vol. 37, no. 4, pp. 289–298, 2001.

[29] A. Hallal, R. Younes, F. Fardoun, and S. Nehme, “Improved analytical model to

predict the effective elastic properties of 2.5D interlock woven fabrics composite,”

Compos. Struct., vol. 94, no. 10, pp. 3009–3028, 2012.

125

[30] A. Hallal, R. Younes, S. Nehme, and F. Fardoun, “A corrective function for the

estimation of the longitudinal Young’s modulus in a developed analytical model

for 2.5D woven composites,” J. Compos. Mater., vol. 45, no. 17, pp. 1793–1804,

2011.

[31] Y. Liu, J. Zhu, Z. Chen, Y. Jiang, C. Li, B. Li, L. Lin, T. Guan, and Z. Chen,

“Mechanical properties and microstructure of 2.5D (shallow straight-joint) quartz

fibers-reinforced silica composites by silicasol-infiltration-sintering,” Ceram. Int.,

vol. 38, pp. 795–800, 2012.

[32] B. K. Behera and R. Mishra, “3-Dimensional weaving,” Indian J. Fibre Text. Res.,

vol. 33, pp. 274–287, 2008.

[33] J. Quinn, R. McIlhagger, and A. T. McIlhagger, “A modified system for design and

analysis of 3D woven preforms,” Compos. Part A Appl. Sci. Manuf., vol. 34, no. 6,

pp. 503–509, 2003.

[34] L. W. Taylor and L. J. Tsai, “An overview on fabrication of three-dimensional

woven textile preforms for composites,” Text. Res. J., vol. 81, no. 9, pp. 932–944,

2011.

[35] Y. Nawab, X. Legrand, and V. Koncar, “Study of changes in 3D-woven multilayer

interlock fabric preforms while forming,” J. Text. Inst., vol. 103, no. 12, pp. 1273–

1279, 2012.

[36] X. Ding and Y. . Lei., “Representation of 3D woven structures by parametric

method,” J. Donghua Univ., vol. 22, no. 1, pp. 22–25, 2005.

[37] H. L. Yi and X. Ding, “Conventional Approach on Manufacturing 3D Woven

Preforms Used for Composites,” J. Ind. Text., vol. 34, no. 1, pp. 39–50, 2004.

[38] C. H. Chiu and C. C. Cheng, “Weaving method of 3D woven preforms for

advanced composite materials,” Text. Res. J., vol. 73, no. 1, pp. 37–41, Jan. 2003.

[39] N. K. Naik and P. D. Prasad, “Stress and faiure analysis of 3D angle interlock

composites,” J. Compos. Mater., 2002.

[40] M. Pankow, C. Yen, M. Rudolph, B. Justusson, D. Zhang, and A. M. Waas,

“Experimental Investigation on the Deformation Response of Hybrid 3D Woven

Composites,” in 53rd Structures, Structural Dynamics and Materials Conference,

2012, pp. 1–19.

[41] R. Muñoz, V. Martínez, C. Federico Sket, González, and Ll. J., “Mechanical

behavior and failure micromechanisms of hybrid 3D woven composites in

tension,” Compos. Part A Appl. Sci. Manuf., vol. 59, pp. 93–104, 2014.

[42] S. Nunna, P. R. Chandra, S. Shrivastava, and a. Jalan, “A review on mechanical

126

behavior of natural fiber based hybrid composites,” J. Reinf. Plast. Compos., vol.

31, no. 11, pp. 759–769, Jun. 2012.

[43] W. Hufenbach, M. Gude, and C. Ebert, “Hybrid 3D-textile reinforced composites

with tailored property profiles for crash and impact applications,” Compos. Sci.

Technol., vol. 69, no. 9, pp. 1422–1426, 2009.

[44] M. Li, S. Wang, Z. Zhang, and B. Wu, “Effect of structure on the mechanical

behaviors of three-dimensional spacer fabric composites,” Appl. Compos. Mater.,

vol. 16, no. 1, pp. 1–14, 2009.

[45] D. sen Li, C. qi Zhao, L. Jiang, and N. Jiang, “Experimental study on the charpy

impact failure of 3D integrated woven spacer composites at room and liquid

nitrogen temperature,” Fibers Polym., vol. 16, no. 4, pp. 875–882, 2015.

[46] M. Umair, “Specialty Fabric Structures,” in Structural Textile Design, Taylor &

Francis Group, 2017, pp. 85–122.

[47] Z. J. Grosicki, Watson’s textile design and colour, 7th ed. London: butter worths

group, 1975.

[48] J. Pascault, H. Sautereau, I. National, J. Verdu, E. Nationale, R. J. J. Williams, and

M. Plata, Thermosetting Polymers, 4th ed. Marcel Decker Inc, USA, 2002.

[49] M. Davallo, H. Pasdar, and M. Mohseni, “Mechanical Properties of Unsaturated

Polyester Resin,” Int. J. ChemTech Res., vol. 2, no. 4, pp. 2113–2117, 2010.

[50] D. Gay, S. V Hoa, and S. W. Tsai, Composite materials. Washington D. C: CRC

Press, 2003.

[51] L. Matějka, “Rheology of epoxy networks near the gel point,” Polym. Bull., vol.

26, no. 1, pp. 109–116, 1991.

[52] D. Ratna, Handbook of Thermoset Resins. ismithers, 2009.

[53] P. Kumar, K. Bhat, B. Rajendra, V. Sharan, and S. Sharma, “An Overview on 3D

Composites – its Definition , Fabrication & Applications,” ICCOMIM-2012, vol.

12, no. 7, pp. 20–26, 2012.

[54] A. Célino, S. Fréour, F. Jacquemin, and P. Casari, “The hygroscopic behavior of

plant fibers: a review,” Front. Chem., vol. 1, no. January, p. 43, Jan. 2013.

[55] D. U. Shah, “Developing plant fibre composites for structural applications by

optimising composite parameters: a critical review,” J. Mater. Sci., vol. 48, no. 18,

pp. 6083–6107, Jun. 2013.

[56] W. D. Brouwer, “Natural fibre composites in structural components: Alternative

applications for sisal?” [Online]. Available:

http://www.fao.org/docrep/004/y1873e/y1873e0a.htm. [Accessed: 01-Jan-2017].

127

[57] C. World, “Fabrication methods.” [Online]. Available:

http://www.compositesworld.com/articles/fabrication-methods. [Accessed: 01-Jan-

2017].

[58] M. Golzar and M. Poorzeinolabedin, “Prototype fabrication of a composite

automobile body based on integrated structure,” no. 12, 2009.

[59] E. Ghassemieh, “Materials in Automotive Application , State of the Art and

Prospects,” in Automotive Industry, InTechopen, 2011, pp. 365–394.

[60] G. Davies, Materials for Automobile Bodies. Elsevier, 2012.

[61] W. Fung and M. Hardcastle, Textiles in automotive engineering, Vol. 13.

Woodhead Publishing, 2001.

[62] J. Brandt, K. Drechslef, and F. Arendtsb, “Mechanical performance of composites

based on various three-dimentional woven-fibre preforms,” Compos. Sci. Technol.,

vol. 56, no. 3, pp. 381–386, 1996.

[63] V. A. Guuenon, T. W. Chou, and J. W. Gillespie, “Toughness properties of a three-

dimensional carbon-epoxy composite,” J. Mater. Sci., vol. 24, no. 11, pp. 4168–

4175, 1989.

[64] S. Stewart and A. Nicholson, “A mechanistic interpretation of the comparative

inplane mechanical properties of 3D woven, stitched and pinned composites,”

Compos. Part A Appl. Sci. antes Part A Appl. Sci. an, vol. 41, no. 6, pp. 709–728,

2010.

[65] L. Tong, A. Mouritz, and M. Bannister, Chapter 2 - Manufacture of 3D fibre

preforms, in 3D Fibre Reinforced Polymer Composites. Elsevier Science: Oxford.

p, 2002.

[66] J. N. Baucom and M. A. Zikry, “Low-velocity impact damage progression in

woven E-glass composite systems,” Compos. Part A Appl. Sci. Manuf., vol. 36, no.

5, pp. 658–664, 2005.

[67] B. Jang, L. Chen, and L. Hwang, “The response of fibrous composites to impact

loading,” … Compos., vol. 11, no. 3, pp. 144–157, 1990.

[68] N. K. Naik, Y. C. Sekher, and S. Meduri, “Damage in woven-fabric composites

subjected to low-velocity impact,” Compos. Sci. Technol., vol. 60, pp. 731–744,

2000.

[69] J. K. Kim and M. L. Sham, “Impact and delamination failure of woven-fabric

composites,” Compos. Sci. Technol., vol. 60, no. 5, pp. 745–761, 2000.

[70] M. V. Hosur, M. Adbullah, and S. Jeelani, “Studies on the low-velocity impact

response of woven hybrid composites,” Compos. Struct., vol. 67, no. 3, pp. 253–

128

262, 2005.

[71] N. K. Naik and Y. C. Sekher, “Damage in Laminated Composites Due to Low

Velocity Impact,” J. Reinf. Plast. Compos., vol. 17, no. 14, pp. 1232–1263, 1998.

[72] B. S. Sugun and R. M. Rao, “Mechanical behavior of woven and multiaxial fabric

comosites,” J. Reinf. Plast. Compos., vol. 19, no. 9, pp. 743–753, 2000.

[73] S. Adanur and C. A. Tam, “On-machine interlocking of 3D laminate structures for

composites *,” Compos. Part B, vol. 28, pp. 497–506, 1997.

[74] T. J. Kang and C. Kim, “Energy-absorption mechanisms in Kevlar multiaxial

warp-knit fabric composites under impact loading,” Compos. Sci. Technol., vol. 60,

pp. 773–784, 2000.

[75] L. C. Mohamed, M. H. Bogdanovich, A. E. Dickinson, J. N. Singletary, and R. B.

Lienhart, “A new generation of 3 D woven fabric preforms and composites,”

Sample J., vol. 37, no. 3, pp. 8–17, 2001.

[76] J. Sen Gupta, “Fracture prediction of a 3D C/C material under impact,” Compos.

Sci. Technol., vol. 65, no. 3–4, pp. 375–386, 2005.

[77] K. Dransfield, C. Baillie, and Y. Mai, “Improving the delamination resistance of

CFRP by stitching—a review,” Compos. Sci. Technol., vol. 50, pp. 305–317, 1994.

[78] A. P. Mouritzas, K. H. Leongb, and I. Herszbergc, “A review of the effect of

stitching on the in-plane mechanical properties of fibre-reinforced polymer

composites,” Compos. Part A, vol. 28, pp. 979–991, 1997.

[79] V. Lopresto, V. Melito, C. Leone, and G. Caprino, “Effect of stitches on the impact

behaviour of graphite / epoxy composites,” Compos. Sci. Technol., vol. 66, pp.

206–214, 2006.

[80] R. Jones, J. Paul, T. E. Tay, and J. F. Williams, “Assessment Of The Effect Of

Impact Damage In Composites: Some Problems And Answers,” Compos. Struct.,

vol. 10, no. 1, pp. 51–73, 1988.

[81] S. Abrate, “impact on laminated composites: recent advances,” Appl. Mech. Rev.,

vol. 47, no. 11, pp. 517–544, 1994.

[82] K. Bilisik, “Multiaxis three-dimensional weaving for composites: A review,” Text.

Res. J., vol. 82, no. 7, pp. 725–743, 2012.

[83] W. J. Cantwell and J. Morton, “The impact resistance of composite materials---a

review,” Composites, vol. 22, no. 5, pp. 347–362, 1991.

[84] S. P. Joshi and C. T. Sun, “Impact induced fracture in a laminated composite,” J.

Compos. Mater., vol. 19, no. 1, pp. 51–66, 1985.

[85] D. Liu and L. E. Malvern, “Matrix Cracking in Impacted Glass/Epoxy Plates,” J.

129


[86] G. A. Bibo and P. J. Hogg, “Review The role of reinforcement architecture on

impact damage mechanisms and post-impact compression behaviour,” J. Mater.

Sci., vol. 31, no. 5, pp. 1115–1137, 1996.

[87] A. Palazotto, L. Gummadi, U. Vaidya, and E. Herup, “Low velocity impact

damage characteristics of Z-fiber reinforced sandwich panels—an experimental

study,” Compos. Struct., vol. 43, pp. 275–288, 1998.

[88] J. Brandt, K. Drechsler, and F.-J. Arendts, “Mechanical performance of composites

based on various three-dimensional woven-fibre preforms,” Compos. Sci. Technol.,

vol. 56, no. 3, pp. 381–386, 1996.

[89] Ko, K. Frank, and D. Hartman, “Impact behavior of 2-D and 3-D Glass/Epoxy

composites,” in Materials Science for the Future: 31 st International SAMPE

Symposium and Exhibition, 1986, p. 1272–1284).

[90] M. O. Richardson and M. J. Wisheart, “Review of low-velocity impact properties

of composite materials,” Compos. Part A, vol. 27, no. 12, pp. 1123–1131, 1996.

[91] L. Tong, A. Mouritz, and M. Bannister, Chapter 5 - 3D woven composites, in 3D

Fibre Reinforced Polymer Composites. Elsevier Science: Oxford, 2002.

[92] S. Adanur, Y. P. Tsao, and C. W. Tam, “Improving fracture resistance of laminar

textile composites by third direction reinforcement,” Compos. Eng., vol. 5, no. 9,

pp. 1149–1158, 1995.

[93] M. De Freitas and L. Reis, “Failure mechanisms on composite specimens subjected

to compression after impact,” Compos. Struct., vol. 42, no. 4, pp. 365–373, 1998.

[94] P. H. Thornton and R. A. Jeryant, “Crash energy management in composite

automotive structures,” Int. J. Impact Eng., vol. 7, no. 2, pp. 167–180, 1988.

[95] H. Y. Choi, H. S. Wang, and F.-K. Chang, “Effect of Laminate Configuration and

Impactor’s Mass on the Initial Impact Damage of Graphite/Epoxy Composite

Plates Due to Line-Loading Impact,” J. Compos. Mater., vol. 26, no. 6, pp. 804–

827, 1992.

[96] H. Y. Choi, H. T. Wu, and F. Chang, “A New Approach toward Understanding

Damage Mechanisms and Mechanics of Laminated Composites Due to Low-

Velocity Impact: Part II-Analysis,” J. Compos. Mater., vol. 25, pp. 1012–1038,

1991.

[97] H. Y. Choi, R. J. Downs, and F. Chang, “A New Approach toward Understanding

Damage Mechanisms and Mechanics of Laminated Composites Due to Low-

Velocity Impact : Part I-Experiments,” J. Compos. Mater., vol. 25, pp. 992–1011,

130

1991.

[98] H. Y. Choi and F. Chang, “A Model for Predicting Damage in Graphite/Epoxy

Laminated Composites Resulting from Low-Velocity Point Impact,” J. Compos.

Mater., vol. 26, no. 14, pp. 2134–2169, 1992.

[99] L. H. Strait, M. L. Karasek, and M. F. Amateau, “Effects of Stacking Sequence on

the Impact Resistance of Carbon Fiber Reinforced Thermoplastic Toughened

Epoxy Laminates,” J. Compos. Mater., vol. 26, no. 12, pp. 1725–1740, 1992.

[100] D. Adams and a Miller, “An analysis of the impact behavior of hybrid composite

materials,” Mater. Sci. Eng., vol. 19, no. 2, pp. 245–260, 1975.

[101] R. Park and J. Jang, “The effects of Hybridization on the mechanical performance

of aramid/polyethylene intraply fabric composites,” Compos. Sci. Technol., vol. 58,

no. 10, pp. 1621–1628, 1998.

[102] D. Short and J. Summerscales, “Hybrids - A review Part 1. Techniques design and

construction,” Compos. Struct., no. October, pp. 215–222, 1979.

[103] D. Short and J. Summerscales, “Hybrids - a review: Part 2. Physical properties,”

Composites, vol. 11, no. 1, pp. 33–38, 1980.

[104] S. S. Cheon, T. S. Lim, and D. G. Lee, “Impact energy absorption characteristics of

glass fiber hybrid composites,” Compos. Struct., vol. 46, no. 3, pp. 267–278, 1999.

[105] G. C. Jacob and J. F. Fellers, “Energy Absorption in Polymer Composites for

Automotive Crashworthiness,” J. Compos. Mater., vol. 36, no. 7, pp. 813–849,

2002.

[106] S. Abrate, Impact on Composite Structures. Cambridge University Press, New

York, 1998.

[107] a Kessler and a K. Bledzki, “Low velocity impact behavior of glass/epoxy cross-

ply laminates with different fiber treatments,” Polym. Compos., vol. 20, no. 2, pp.

269–278, 1999.

[108] M. Aktas, R. Karakuzu, and Y. Arman, “Compression-after impact behavior of

laminated composite plates subjected to low velocity impact in high temperatures,”

Compos. Struct., vol. 89, no. 1, pp. 77–82, 2009.

[109] Y. Luo, L. Lv, B. Sun, Y. Qiu, and B. Gu, “Transverse impact behavior and energy

absorption of three-dimensional orthogonal hybrid woven composites,” Compos.

Struct., vol. 81, no. 2, pp. 202–209, 2007.

[110] L. Lv, B. Sun, Y. Qiu, and B. Gu, “Energy Absorptions and Failure Modes of 3D

Orthogonal Hybrid Woven Composite Struck by Flat-Ended Rod,” Polym.

Compos., vol. 27, no. 4, pp. 410–416, 2006.

131

[111] R. Gerlach, C. R. Siviour, J. Wiegand, and N. Petrinic, “In-plane and through-

thickness properties, failure modes, damage and delamination in 3D woven carbon

fibre composites subjected to impact loading,” Compos. Sci. Technol., vol. 72, no.

3, pp. 397–411, 2012.

[112] R. King, G. Stewart, A. McIlhagger, and J. Quinn, “The influence of throughthe-

thickness binder yarn count on fibre volume fraction ,crimp, and damage tolerance

within 3D woven carbon fibre composites,” Polym. Polym. Compos., vol. 17, no. 5,

p. 313, 2009.

[113] N. V. Padaki, R. Alagirusamy, B. L. Deopura, and R. Fangueiro, “Influence of

Preform Interlacement on the Low Velocity Impact Behavior of Multilayer Textile

Composites,” J. Ind. Text., vol. 40, no. 2, pp. 171–185, 2010.

[114] F. Chen and J. M. Hodgkinson, “Impact behaviour of composites with different

fibre architecture,” in Proceedings of the Institution of Mechanical Engineers, Part

G: Journal of Aerospace Engineering, 2009, vol. 223, no. 7, pp. 1009–1017.

[115] P. Potluri, P. Hogg, M. Arshad, D. Jetavat, and P. Jamshidi, “Influence of fibre

architecture on impact damage tolerance in 3D woven composites,” Appl. Compos.

Mater., vol. 19, no. 5, pp. 799–812, 2012.

[116] Wang, Youjiang, and Z. Dongming, “Effect of fabric structures on the mechanical

properties of 3-D textile composites,” J. Ind. Text., vol. 35, no. 3, pp. 239–256,

2006.

[117] Y. Mahadik and S. R. Hallett, “Effect of fabric compaction and yarn waviness on

3D woven composite compressive properties,” Compos. Part A Appl. Sci. Manuf.,

vol. 42, no. 11, pp. 1592–1600, 2011.

[118] S. Kari, M. Kumar, I. Jones, N. Warrior, and A. Long, “Effect of yarn cross-

sectional shapes and crimp on the mechanical properties of 3D woven composites,”

in Proceedings of the 17th IFAC World Congress, 2008, pp. 1–10.

[119] Farley and L. Gary, “A mechanism responsible for reducing compression strength

of through-the-thickness reinforced composite material,” J. Compos. Mater., vol.

26, no. 12, pp. 1784–1795, 1992.

[120] B. N. Cox, M. S. Dadkhah, R. V. Inman, W. L. Morris, and J. Zupon,

“Mechanisms of compressive failure in 3D composites,” Acta Metall. Mater., vol.

40, no. 12, pp. 3285–3298, 1992.

[121] E. Demuts, R. S. Whitehead, and R. B. Deo, “Assesment of Damage Tolerance in

Composites *,” Compos. Struct., vol. 4, no. 1, pp. 45–58, 1985.

[122] J. N. Baucom and M. A. Zikry, “Evolution of Failure Mechanisms in 2D and 3D

132

Woven Composite Systems Under Quasi-Static Peforation,” J. Compos. Mater.,

vol. 37, no. 18, pp. 1651–1674, 2003.

[123] J. N. Baucom and M. A. Zikry, “Low-velocity impact damage progression in

woven Eglass composite systems,” Compos. Part A Appl. Sci. Manuf., vol. 36, no.

5, pp. 658–664, 2005.

[124] Y. a. Bahei-El-Din and M. a. Zikry, “Impact-induced deformation fields in 2D and

3D woven composites,” Compos. Sci. Technol., vol. 63, no. 7, pp. 923–942, 2003.

[125] P. M. Schubel, J.-J. Luo, and I. M. Daniel, “Impact and post impact behavior of

composite sandwich panels,” Compos. Part A Appl. Sci. Manuf., vol. 38, no. 3, pp.

1051–1057, 2007.

[126] E. G. Guynn and T. K. O’Brien, “The influence of lay-up and thickness on

composite impact damage and compression strength.,” in Guynn, E. G., and T. K.

O’Brien. “The influence of lay-up and thickness on composite impact damage and

compression strength.” Proc 26th AIAA/ASME/ASCE/AHS/ASC Structures,

Structural dynamics and Materials Conf, 1985, pp. 187–196.

[127] P. T. Curtis, J. Gates, and C. G. Molyneux, “Impact damage growth in carbon fibre

composites,” ., 1993.

[128] S. A. Hitchen and R. M. Kemp, “Hitchen, S. A., and R. M. Kemp. The effect of

stacking sequence and layer thickness on the compressive behaviour of carbon

composite materials: impact damage and compression after impact.,” 1994.

[129] C. Soutis and P. T. Curtis, “Prediction of the post-impact compressive strength of

CFRP laminated composites,” Compos. Sci. Technol., vol. 56, no. 6, pp. 677–684,

1996.

[130] X. Zhang, G. A. O. Davies, and D. Hitchings, “Impact damage with compressive

preload and post-impact compression of carbon composite plates,” Int. J. Mater.

FormingInternational J. Impact Eng., vol. 22, no. 5, pp. 485–509, 1999.

[131] D. A. Wyrick and D. F. Adams, “Residual strength of a carbon/epoxy composite

material subjected to repeated impact,” J. Compos. Mater., vol. 22, no. 8, pp. 749–

765, 1988.

[132] S. I. Ibekwe, P. F. Mensah, G. Li, S. Pang, and M. A. Stubblefield, “Impact and

post impact response of laminated beams at low temperatures,” Compos. Struct.,

vol. 79, pp. 12–17, 2007.

[133] A. M. El-Habak, “Effect of impact perforation load on GFRP composites,”

Composites, vol. 24, no. 4, pp. 341–345, 1993.

[134] S. J. Park, M. K. Seo, T. J. Ma, and D. R. Lee, “Effect of chemical treatment of

133

Kevlar fibers on mechanical interfacial properties of composites.,” J. Colloid

Interface Sci., vol. 252, no. 1, pp. 249–255, 2002.

[135] P. Potluri, T. Sharif, D. Jetavat, A. Aktas, R. Choudhry, P. Hogg, A. Foreman, G.

Stringer, and L. Starink, “Bench-marking of 3D preforming strategies,” in 17th

International Conferences on Composite Materials (ICCM-17), 2009.

[136] S. Dhiman, P. Potluri, and C. Silva, “Influence of binder configuration on 3D

woven composites,” Compos. Struct., vol. 134, pp. 862–868, 2015.

[137] M. N. Saleh, G. Lubineau, P. Potluri, P. J. Withers, and C. Soutis, “Micro-

mechanics based damage mechanics for 3D orthogonal woven composites:

Experiment and numerical modelling,” Compos. Struct., vol. 156, pp. 115–124,

2016.

[138] A. W. Van Vuure, J. A. Ivens, and I. Verpoest, “Mechanical properties of

composite panels based on woven sandwich- fabric preforms,” Compos. - Part A

Appl. Sci. Manuf., vol. 31, no. 7, pp. 671–680, 2000.

[139] H. Judawisastra, J. Ivens, and I. Verpoest, “The fatigue behaviour and damage

development sandwich composites,” Compos. Struct., vol. 43, no. 1, pp. 35–45,

1998.

[140] M. V. Hosur, M. Abdullah, and S. Jeelani, “Manufacturing and low-velocity

impact characterization of hollow integrated core sandwich composites with hybrid

face sheets,” Compos. Struct., vol. 69, no. 2, pp. 167–181, 2005.

[141] M. V. Hosur, M. Abdullah, and S. Jeelani, “Manufacturing and low-velocity

impact characterization of hollow integrated core sandwich composites with hybrid

face sheets,” Compos. Struct., vol. 65, no. 1, pp. 103–115, 2004.

[142] C. Q. Zhao, D. Sen Li, T. Q. Ge, L. Jiang, and N. Jiang, “Experimental study on

the compression properties and failure mechanism of 3D integrated woven spacer

composites,” Mater. Des., vol. 56, pp. 50–59, 2014.

[143] D. Sen Li, C. Q. Zhao, N. Jiang, and L. Jiang, “Fabrication, properties and failure

of 3D integrated woven spacer composites with thickened face sheets,” Mater.

Lett., vol. 148, pp. 103–105, 2015.

[144] H. Fan, Q. Zhou, W. Yang, and Z. Jingjing, “An experiment study on the failure

mechanisms of woven textile sandwich panels under quasi-static loading,”

Compos. Part B, vol. 41, no. 8, pp. 686–692, 2010.

[145] N. Khokar, “3D fabric-forming processes: distinguishing between 2D-weaving,

3D-weaving and an unspecified non-interlacing process,” J. Text. Inst., vol. 87, no.

1, pp. 97–106, 1997.

134

[146] N. Khokar, “3D-Weaving: Theory and Practice,” J. Text. Inst., vol. 92, no. 2, pp.

193–207, 2001.

[147] P. M. Wambua and R. Anandjiwala, “A Review of Preforms for the Composites

Industry,” J. Ind. Text., vol. 40, no. 4, pp. 310–333, Jul. 2010.

[148] B. K. Behera and R. Mishra, “3-Dimensional weaving,” Indian J. Fibre Text. Res.,

vol. 33, pp. 274–287, 2008.

[149] Y. Bahei-El-Din and M. Zikry, “Impact-induced deformation fields in 2D and 3D

woven composites,” Compos. Sci. Technol., vol. 63, pp. 923–942, 2003.

[150] C.-H. Chiu and C.-C. Cheng, “Weaving Method of 3D Woven Preforms for

Advanced Composite Materials,” Text. Res. J., vol. 73, no. 1, pp. 37–41, 2003.

[151] M. Umair, Y. Nawab, and M. H. Malik, “Development and characterization of

three-dimensional woven-shaped preforms and their associated composites,” J.

Reinf. Plast. Compos., vol. 34, no. 24, pp. 2018–2028, 2015.

[152] X. Chen, M. Spola, J. G. Paya, and P. Mollst, “Experimental Studies on the

Structure and Mechanical Properties of Multi-layer and Angle-interlock Woven

Structures,” J. Text. Inst., vol. 90, no. 1, pp. 91–99, 2009.

[153] X. Chen, R. T. Knox, D. F. Mckenna, and R. Mather, “Relation between linear

linkage and mechanical properties of 3D woven textile structures,” in Technical

Research Centre of Finland: Textiles and Composites, 1992, pp. 166–172.

[154] S. Dai, P. R. Cunningham, S. Marshall, and C. Silva, “Influence of fibre

architecture on the tensile , compressive and flexural behaviour of 3D woven

composites,” Compos. PART A, vol. 69, pp. 195–207, 2015.

[155] D. Zhang, A. M. Waas, and C. F. Yen, “Progressive damage and failure response

of hybrid 3D textile composites subjected to flexural loading, part I: Experimental

studies,” Int. J. Solids Struct., vol. 1, pp. 1–12, 2015.

[156] D. Zhang, A. M. Waas, and C. F. Yen, “Progressive damage and failure response

of hybrid 3D textile composites subjected to flexural loading, part II: Mechanics

based multiscale computational modeling of progressive damage and failure,” Int.

J. Solids Struct., vol. 1, pp. 321–335, 2015.

[157] P. Turner, T. Liu, and X. Zeng, “Collapse of 3D orthogonal woven carbon fibre

composites under in-plane tension / compression and out-of-plane bending,”

Compos. Struct., vol. 142, pp. 286–297, 2016.

[158] P. Tan, L. Tong, G. P. Steven, and T. Ishikawa, “Behavior of 3D orthogonal woven

CFRP composites . Part I . Experimental investigation,” Compos. Part A, vol. 31,

no. 3, pp. 259–271, 2000.

135

[159] M. Nasr, A. Yudhanto, P. Potluri, G. Lubineau, and C. Soutis, “Characterising the

loading direction sensitivity of 3D woven composites : Effect of z-binder

architecture,” Compos. Part A, vol. 90, pp. 577–588, 2016.

[160] A. Kumar, V. V Chavan, S. Ahmad, and R. Alagirusamy, “Low velocity impact

response of 2D and 3D Kevlar / polypropylene composites,” Int. J. Impact Eng.,

vol. 93, pp. 136–143, 2016.

[161] K. Bilisik, “Multiaxis 3D Woven Preform and Properties of Multiaxis 3D Woven

and 3D Orthogonal Woven Carbon/Epoxy Composites,” J. Reinf. Plast. Compos.,

vol. 29, no. 8, pp. 1173–1186, 2010.

[162] S. Rudov-Clark and A. P. Mouritz, “Tensile fatigue properties of a 3D orthogonal

woven composite,” Compos. Part A, vol. 39, no. 6, pp. 1018–1024, 2008.

[163] R. Mishra, V. Baheti, B. K. Behera, and J. Militky, “Novelties of 3-D woven

composites and nanocomposites,” J. Text. Inst., vol. 105, no. 1, pp. 84–92, 2014.

[164] R. Mishra, “Specific functional properties of 3D woven glass nanocomposites,” J.


[165] Y. Liu, J. Zhu, Z. Chen, Y. Jiang, B. Li, L. Lin, T. Guan, X. Cong, and C. Li,

“Mechanical behavior of 2.5D (shallow bend-joint) and 3D orthogonal quartz f /

silica composites by silicasol-infiltration-sintering,” Mater. Sci. Eng. A, vol. 532,

pp. 230–235, 2012.

[166] B. K. Behera and B. P. Dash, “Mechanical behavior of 3D woven composites,”

Mater. Des., vol. 67, pp. 261–271, 2015.

[167] H. Alhussein, R. Umer, S. Rao, E. Swery, S. Bickerton, and W. J. Cantwell,

“Characterization of 3D woven reinforcements for liquid composite molding

processes,” J. Mater. Sci., vol. 51, no. 6, pp. 3277–3288, 2016.

[168] F. Dau, M. L. Dano, and Y. Duplessis-Kergomard, “Experimental investigations

and variability considerations on 3D interlock textile composites used in low

velocity soft impact loading,” Compos. Struct., vol. 153, pp. 369–379, 2016.

[169] B. Yu, R. S. Bradley, C. Soutis, P. J. Hogg, and P. J. Withers, “2D and 3D imaging

of fatigue failure mechanisms of 3D woven composites,” Compos. Part A Appl.

Sci. Manuf., vol. 77, pp. 37–49, 2015.

[170] A. Shigang, F. Daining, H. Rujie, and P. Yongmao, “Effect of manufacturing

defects on mechanical properties and failure features of 3D orthogonal woven C/C

composites,” Compos. Part B, vol. 71, pp. 113–121, 2015.

[171] N. Gokarneshan and R. Alagirusamy, “Weaving of 3D fabrics: A critical

appreciation of the developments,” Text. Prog., vol. 41, no. 1, pp. 1–58, Apr. 2009.

136

[172] X. Chen, Advances in 3D Textiles. Cambridge, England: Woodhead Publishing

Limited, 2015.

[173] W. T. Miller and R. H. Pusch, “Woven multi-layer angle interlock fabrics and

methods of making same,” EP 0 422,293 A1, 1991.

[174] W. T. Miller, D. P. Calamito, and R. H. Push, “Woven multi-layer angle interlock

fabrics having fill weaver yarns interwoven with relatively straight extending warp

yarns,” 4,958,663, 1990.

[175] “[http://texgen.sourceforge.net/].” .

[176] J. Schultz and C. Martin, “The Role of the Interface in Carbon Fibre-Epoxy

Compositest,” J. Adhes., vol. 23, no. 1, pp. 45–60, 1987.

[177] S. Zhandarov and E. Mäder, “Characterization of fiber/matrix interface strength:

Applicability of different tests, approaches and parameters,” Compos. Sci.

Technol., vol. 65, no. 1, pp. 149–160, 2005.

[178] J.-K. Kim and Y.-W. Mai, “High strength, high fracture toughness fibre

composites with interface control - a review,” Compos. Sci. Technol., vol. 41, pp.

333–378, 1991.

[179] H. M. Taylor, “Tensile and Tearing Strength of Cotton Cloths,” J. Text. Inst.

Trans., vol. 50, no. 1, pp. T161–T188, 1959.

[180] W. Ashraf, Y. Nawab, M. Umair, and K. Shaker, “Investigation of mechanical

behavior of woven / knitted hybrid composites,” J. Text. Inst., pp. 1–8, 2016.

[181] F. Stig and S. Hallström, “Influence of crimp on 3D-woven fibre reinforced

composites,” Compos. Struct., vol. 95, pp. 114–122, 2013.

[182] J. N. Baucom, M. A. Zikry, and A. M. Rajendran, “Low-velocity impact damage

accumulation in woven S2-glass composite systems,” Compos. Sci. Technol., vol.

66, no. 10, pp. 1229–1238, 2006.

[183] S. Chou, H. Chen, and H. Chen, “Effect of weave structure on mechanical fracture

behavior of three-dimensional carbon fiber fabric reinforced epoxy resin

composites,” Compos. Sci. Technol., vol. 45, no. 1, pp. 23–35, 1992.

[184] Z. Y. Zhang and M. O. W. Richardson, “Low velocity impact induced damage

evaluation and its effect on the residual flexural properties of pultruded GRP

composites,” Compos. Struct., vol. 81, no. 2, pp. 195–201, 2007.

[185] D. P. C. Aiman, M. F. Yahya, J. Salleh, S. Alam, and S. D. Ehsan, “Impact

Properties of 2D and 3D Woven Composites : A Review,” in International

Conference on Advanced Science, Engineering and Technology, 2015, vol. 20002,

pp. 20002-1-6.

137

[186] S. H. Aziz and M. P. Ansell, “The effect of alkalization and fibre alignment on the

mechanical and thermal properties of kenaf and hemp bast fibre composites: Part 1

- polyester resin matrix,” Compos. Sci. Technol., vol. 64, no. 9, pp. 1219–1230,

2004.

[187] X. Lei, W. Rui, Z. Shujie, and L. Yong, “Vibration characteristics of glass

fabric/epoxy composites with different woven structures,” J. Compos. Mater., vol.

45, no. 10, pp. 1069–1076, 2011.

[188] D. Kaka, J. Rongong, A. Hodzic, and C. Lord, “Dynamic mechanical properties of

woven carbon fibre reinforced thermoplastic composite,” in 20th International

Conference on Composite Materials, 2015, pp. 1–13.

[189] B. P. Dash and B. K. Behera, “A study on structure property relationship of 3D

woven composites,” in Materials Today: Proceedings, 2015, vol. 2, pp. 2991–

3007.

[190] M. Koyuncu, M. Karahan, N. Karahan, K. Shaker, and Y. Nawab, “Static and

dynamic mechanical properties of cotton/epoxy green composites,” Fibres Text.

East. Eur., vol. 24, no. 4, pp. 105–111, 2016.

[191] X. Chen, W. Lo, and A. E. Tayyar, “Mouldability of Angle-Interlock Woven

FabricsforTechnical Applications,” Text. Res. J., vol. 72, no. 3, pp. 195–200, 2002.

[192] H. Jinlian, 3-D fibrous assemblies, 1st ed. Woodhead Publishing Limited, 2008.

[193] X. Chen, L. W. Taylor, and L. J. Tsai, “An Overview on Fabrication of Three-

Dimensional Woven Textile Preforms for Composites,” Text. Res. J., vol. 81, no.

9, pp. 932–944, 2011.

[194] K. Bilisik and M. H. Mohamed, “Multiaxis Three-dimensional Flat Woven

Preform (Tube Rapier Weaving) and Circular Woven Preform (Radial Crossing

Weaving)*,” Text. Res. J., vol. 79, no. 12, pp. 1067–1084, 2009.

[195] K. Bilisik and M. H. Mohamed, “Multiaxis Three-Dimensional Flat Woven

Preforms - Tube Carrier Weaving,” Text. Res. J., vol. 80, no. 8, pp. 696–711, 2010.

[196] K. Bilisik, “Multiaxial Three-Dimensional (3-D) Circular Woven Fabric,” US

Patent: 6,129,122, 2000.

[197] M. H. Mohamed and K. Bilisik, “Multi-layer Three-Dimensional Fabric and

Method for Producing,” US Patent: 5,465,760, 1995.

[198] R. Gerlach, C. R. Siviour, J. Wiegand, and N. Petrinic, “In-plane and through-

thickness properties, failure modes, damage and delamination in 3D woven carbon

fibre composites subjected to impact loading,” Compos. Sci. Technol., vol. 72, no.

3, pp. 397–411, 2012.

138

[199] M. Pankow, B. Justusson, A. Salvi, A. Waas, C. F. Yen, and S. Ghiorse, “Shock

response of 3D woven composites: An experimental investigation,” Compos.

Struct., vol. 93, no. 5, pp. 1337–1346, 2011.

[200] B. K. Behera and B. P. Dash, “An experimental investigation into the mechanical

behaviour of 3D woven fabrics for structural composites,” Fibers Polym., vol. 15,

no. 9, pp. 1950–1955, 2014.

[201] K. C. Warren, R. A. Lopez-Anido, and J. Goering, “Experimental investigation of

three-dimensional woven composites,” Compos. Part A Appl. Sci. Manuf., vol. 73,

pp. 242–259, 2015.

[202] T. Gao, Y. Zhao, G. Zhou, Y. Han, Y. Zheng, Z. Shan, D. Hui, F. Xu, and Y. Qiu,

“Fabrication and characterization of three dimensional woven carbon fiber/silica

ceramic matrix composites,” Compos. Part B Eng., vol. 77, pp. 122–128, 2015.

[203] V. Herb, E. Martin, and G. Couégnat, “Damage analysis of thin 3D-woven SiC/SiC

composite under low velocity impact loading,” Compos. Part A Appl. Sci. Manuf.,

vol. 43, no. 2, pp. 247–253, 2012.

[204] Y. Tang, B. Sun, and B. Gu, “Impact Damage of 3D Cellular Woven Composite

from Unit-cell Level Analysis,” Int. J. Damage Mech., vol. 20, no. 3, pp. 323–346,

2011.

[205] L. Yao, Q. Rong, Z. Shan, and Y. Qiu, “Static and bending fatigue properties of

ultra-thick 3D orthogonal woven composites,” J. Compos. Mater., vol. 47, no. 5,

pp. 569–577, 2013.

[206] D. Li, D. Fang, G. Zhang, and H. Hu, “Effect of temperature on bending properties

and failure mechanism of three-dimensional braided composite,” Mater. Des., vol.

41, pp. 167–170, 2012.

[207] M. N. Saleh, A. Yudhanto, P. Potluri, G. Lubineau, and C. Soutis, “Characterising

the loading direction sensitivity of 3D woven composites: Effect of z-binder

architecture,” Compos. Part A Appl. Sci. Manuf., vol. 90, pp. 577–588, 2016.

[208] P. Turner, T. Liu, and X. Zeng, “Dynamic Response of Orthogonal Three-

Dimensional Woven Carbon Composite Beams Under Soft Impact,” J. Appl.

Mech., vol. 82, no. 12, p. 121008, 2015.

[209] A. E. Bogdanovich, M. Karahan, S. V. Lomov, and I. Verpoest, “Quasi-static

tensile behavior and damage of carbon/epoxy composite reinforced with 3D non-

crimp orthogonal woven fabric,” Mech. Mater., vol. 62, pp. 14–31, 2013.

[210] A. Hallal, R. Younes, S. Nehme, and F. Fardoun, “A corrective function for the

estimation of the longitudinal Young’s modulus in a developed analytical model

139

for 2.5D woven composites,” J. Compos. Mater., vol. 45, no. 17, pp. 1793–1804,

2011.

[211] S. Dai, P. R. Cunningham, S. Marshall, and C. Silva, “Open hole quasi-static and

fatigue characterisation of 3D woven composites,” Compos. Struct., vol. 131, pp.

765–774, 2015.

[212] B. Yu, R. Blanc, C. Soutis, and P. J. Withers, “Evolution of damage during the

fatigue of 3D woven glass-fibre reinforced composites subjected to tension-tension

loading observed by time-lapse X-ray tomography,” Compos. Part A Appl. Sci.

Manuf., vol. 82, pp. 279–290, 2016.

[213] R. Seltzer, C. González, R. Muñoz, J. Llorca, and T. Blanco-Varela, “X-ray

microtomography analysis of the damage micromechanisms in 3D woven

composites under low-velocity impact,” Compos. Part A Appl. Sci. Manuf., vol. 45,

pp. 49–60, 2013.

[214] M. Karahan, S. V. Lomov, A. E. Bogdanovich, and I. Verpoest, “Fatigue tensile

behavior of carbon/epoxy composite reinforced with non-crimp 3D orthogonal

woven fabric,” Compos. Sci. Technol., vol. 71, no. 16, pp. 1961–1972, 2011.

[215] L. Jin, H. Hu, B. Sun, and B. Gu, “Three-point bending fatigue behavior of 3D

angle-interlock woven composite,” J. Compos. Mater., vol. 46, no. 8, pp. 883–894,

2012.

[216] L. Jin, Z. Niu, B. C. Jin, B. Sun, and B. Gu, “Comparisons of static bending and

fatigue damage between 3D angle-interlock and 3D orthogonal woven

composites,” J. Reinf. Plast. Compos., vol. 31, no. 14, pp. 935–945, 2012.

[217] K. Bilisik, N. S. Karaduman, N. E. Bilisik, and H. E. Bilisik, “Three-dimensional

fully interlaced woven preforms for composites,” Text. Res. J., vol. 83, no. 19, pp.

2060–2084, 2013.

[218] G. Stegschuster, K. Pingkarawat, B. Wendland, and A. P. Mouritz, “Experimental

determination of the mode i delamination fracture and fatigue properties of thin 3D

woven composites,” Compos. Part A Appl. Sci. Manuf., vol. 84, pp. 308–315,

2016.

[219] S. Dai, P. R. Cunningham, S. Marshall, and C. Silva, “Influence of fibre

architecture on the tensile, compressive and flexural behaviour of 3D woven

composites,” Compos. Part A Appl. Sci. Manuf., vol. 69, pp. 195–207, 2015.

[220] B. K. Behera and B. P. Dash, “An experimental investigation into structure and

properties of 3D-woven aramid and PBO fabrics,” J. Text. Inst., vol. 104, no. 12,

pp. 1337–1344, 2013.

140

[221] A. M. Coppola, P. R. Thakre, N. R. Sottos, and S. R. White, “Tensile properties

and damage evolution in vascular 3D woven glass/epoxy composites,” Compos.

Part A Appl. Sci. Manuf., vol. 59, pp. 9–17, 2014.

[222] L. Li, S. V. Lomov, X. Yan, and V. Carvelli, “Cluster analysis of acoustic emission

signals for 2D and 3D woven glass/epoxy composites,” Compos. Struct., vol. 116,

pp. 286–299, 2014.

[223] T. Hamouda, A.-F. M. Seyam, and K. Peters, “Polymer optical fibers integrated

directly into 3D orthogonal woven composites for sensing,” Smart Mater. Struct.,

vol. 24, no. 2, p. 25027, 2015.

[224] T. Hamouda, A. F. M. Seyam, and K. Peters, “Evaluation of the integrity of 3D

orthogonal woven composites with embedded polymer optical fibers,” Compos.

Part B Eng., vol. 78, pp. 79–85, 2015.

[225] M. Castellucci, S. Klute, E. M. Lally, M. E. Froggatt, and D. Lowry, “Three-Axis

Distributed Fiber Optic Strain Measurement in 3D Woven Composite Structures,”

in Proc SPIE 8690, Industrial and Commercial Applications of Smart Structures

Technologies, 2013, pp. 1–13.

[226] S. Nauman, I. Cristian, and V. Koncar, “Intelligent carbon fibre composite based

on 3D-interlock woven reinforcement,” Text. Res. J., vol. 82, no. 9, pp. 931–944,

2012.

[227] W. D. Brouwer, “Natural fibre composites in structural components: alternative

applications for Sisal,” in Seminar, Commond Fund for Commodities-Alternative

Applications for Sisal and Henecuen, 2000.

[228] W. D. Brouwer, “Natural fibre composites in structural components, alternative for

sisal,” in joint FAO/CFC Seminar, 2000.

[229] S. Rwawiire, B. Tomkova, J. Militky, A. Jabbar, and B. M. Kale, “Development of

a biocomposite based on green epoxy polymer and natural cellulose fabric (bark

cloth) for automotive instrument panel applications,” Compos. Part B Eng., vol.

81, pp. 149–157, 2015.

[230] V. Fombuena, L. Bernardi, O. Fenollar, T. Boronat, and R. Balart,

“Characterization of green composites from biobased epoxy matrices and bio-

fillers derived from seashell wastes,” Mater. Des., vol. 57, pp. 168–174, 2014.

[231] L. Di Landro and G. Janszen, “Composites with hemp reinforcement and bio-based

epoxy matrix,” Compos. Part B, vol. 67, pp. 220–226, 2014.

[232] Z. Aslan and Y. Alnak, “Characterization of Interlaminar Shear Strength of

Laminated Woven E-Glass / Epoxy Composites by Four Point Bend Shear Test,”

141

Polym. Compos., vol. 31, no. 2, pp. 359–368, 2010.

[233] F. Sarasini, J. Tirillò, L. Ferrante, M. Valente, T. Valente, L. Lampani, P.

Gaudenzi, S. Cioffi, S. Iannace, and L. Sorrentino, “Drop-weight impact behaviour

of woven hybrid basalt-carbon/epoxy composites,” Compos. Part B Eng., vol. 59,

pp. 204–220, 2014.

[234] R. King, G. Stewart, A. McIlhagger, and J. Quinn, “The Influence of Through-The-

Thickness Binder Yarn Count on Fibre Volume Fraction, Crimp and Damage

Tolerance Within 3D Woven Carbon Fibre Composites,” Polym. Polym. Compos.,

vol. 17, no. 5, pp. 303–312, 2009.

[235] N. M. Barkoula, B. Alcock, N. O. Cabrera, and T. Peijs, “Characterization of

Multi-stitched Woven Nano Composites Under Compression After Low Velocity

Impact (CALVI) Load,” Polym. Compos., 2017.

[236] G. Erdogan and K. Bilisik, “Compression after low-velocity impact (CAI)

properties of multi-stitched composites,” Mech. Adv. Mater. Struct., vol. 25, no. 8,

pp. 623–636, 2018.

[237] P. Potluri, E. Kusak, and T. Y. Reddy, “Novel stitch-bonded sandwich composite

structures,” Compos. Struct., vol. 59, no. 2, pp. 251–259, 2003.

[238] M. V. Hosur, M. Abdullah, and S. Jeelani, “Dynamic compression behavior of

integrated core sandwich composites,” Mater. Sci. Eng. A, vol. 445, pp. 54–64,

2007.

[239] U. Vaidya, S. Nelson, B. Sinn, and B. Mathew, “Processing and high strain rate

impact response of multi-functional sandwich composites,” Compos. Struct., vol.

52, no. 3–4, pp. 429–440, 2001.

[240] P. Robinson and G. A. O. Davies, “Impactor mass and specimen geometry effects

in low velocity impact of laminated composites,” Int. J. Impact Eng., vol. 12, no. 2,

pp. 189–207, 1992.

[241] D. D. Cartié and N. A. Fleck, “The effect of pin reinforcement upon the through-

thickness compressive strength of foam-cored sandwich panels,” Compos. Sci.

Technol., vol. 63, no. 16, pp. 2401–2409, 2003.

[242] M. C. Rice, C. A. Fleischer, and M. Zupan, “Study on the collapse of pin-

reinforced foam sandwich panel cores,” Exp. Mech., vol. 46, no. 2, pp. 197–204,

2006.

[243] I. Zic, M. P. Ansell, A. Newton, and R. W. Price, “Mechanical Properties of

Composite Panels Reinforced with Integrally Woven 3-D Fabrics,” J. Text. Inst.,

vol. 81, no. 4, pp. 461–479, 1990.

142

[244] F. Jin, H. Chen, L. Zhao, H. Fan, C. Cai, and N. Kuang, “Failure mechanisms of

sandwich composites with orthotropic integrated woven corrugated cores:

Experiments,” Compos. Struct., vol. 98, pp. 53–58, 2013.

[245] H. Judawisastra, J. Ivens, and I. Verpoest, “The fatigue behaviour and damage

development sandwich composites,” Compos. Struct., vol. 43, no. 1, pp. 35–45,

1998.

[246] A. Mountasir, G. Hoffmann, C. Cherif, M. Löser, A. Mühl, and K. Großmann,

“Development of non-crimp multi-layered 3D spacer fabric structures using hybrid

yarns for thermoplastic composites,” Procedia Mater. Sci., vol. 2, pp. 10–17, 2013.

[247] A. Mountasir, G. Hoffmann, and C. Cherif, “Development of weaving technology

for manufacturing three-dimensional spacer fabrics with high-performance yarns

for thermoplastic composite applications: An analysis of two-dimensional

mechanical properties,” Text. Res. J., vol. 81, no. 13, pp. 1354–1366, 2011.

[248] A. Mountasir, G. Hoffmann, C. Cherif, M. Loser, and K. Grobmann, “Competitive

manufacturing of 3D thermoplastic composite panels based on multi-layered

woven structures for lightweight engineering,” Compos. Struct., vol. 133, pp. 415–

424, 2015.

[249] S. Wang, M. Li, Z. Zhang, and B. Wu, “Properties of Facesheet-reinforced 3-D

Spacer Fabric Composites and the Integral Multi-facesheet Structures,” J. Reinf.

Plast. Compos., vol. 29, no. 6, pp. 793–806, 2010.

[250] M. Ashir, C. Sennewald, and G. Hoffmann, “Development of Woven Spacer

Fabrics Based on Steel Wires and Carbon Rovings,” Fibres Text. East. Eur., vol. 1,

no. 121, pp. 49–55, 2017.

[251] X. Hou, H. Hu, and V. V Silberschmidt, “A study of computational mechanics of

3D spacer fabric : factors affecting its compression deformation,” J. Mater. Sci.,

vol. 47, no. 9, pp. 3989–3999, 2012.

[252] M. Sadighi and S. A. Hosseini, “Finite element simulation and experimental study

on mechanical behavior of 3D woven glass fiber composite sandwich panels,”

Compos. Part B Eng., vol. 55, pp. 158–166, 2013.

[253] A. Corigliano, E. Rizzi, and E. Papa, “Experimental characterization and numerical

simulations of a syntactic-foam / glass- fibre composite sandwich,” Compos. Sci.

Technol., vol. 60, no. 11, pp. 2169–2180, 2000.

[254] M. Avalle, G. Belingardi, and R. Montanini, “Characterization of polymeric

structural foams under compressive impact loading by means of energy-absorption

diagram,” Int. J. Impact Eng., vol. 25, no. 5, pp. 455–472, 2001.

143

[255] A. W. Van Vuure, J. A. Ivens, and I. Verpoest, “Mechanical properties of

composite panels based on woven sandwich-fabric preforms,” Compos. Sci.

Technol., vol. 60, no. 8, pp. 1263–1276, 2000.

[256] P. A. Engel, Impact wear of materials, 2nd ed. Elsevier, 1978.

[257] J. Suhr, P. Victor, L. Ci, S. Sreekala, X. Zhang, O. Nalamasu, and P. M. Ajayan,

“Fatigue resistance of aligned carbon nanotube arrays under cyclic compression,”

Nat. Nanotechnol., vol. 2, no. 7, pp. 417–421, 2007.

144

7 APPENDIX

APPENDIX 2.1

Weave design of 3D orthogonal layer to layer warp interlock

145

APPENDIX 2.2

Weave design of 3D orthogonal layer to layer weft interlock

146

APPENDIX 2.3

Weave design of 3D orthogonal layer to layer bidirectional interlock

147

APPENDIX 3.1

Weave design of 3D orthogonal layer to layer interlock, F1(OLL)

148

APPENDIX 3.2

Weave design of orthogonal through thickness interlock, F2(OTT)

149

APPENDIX 3.3

Weave design of layer to layer angle interlock, F3(ALL)

150

APPENDIX 3.4

Weave design of through thickness angle interlock, F4(ATT)

151

APPENDIX 3.5

Weave design of hybrid 1, F5(H1)

152

APPENDIX 3.6


153

APPENDIX 3.7


154

APPENDIX 3.8

Reference for mean curve of results

0

5

10

15

20

25

30

0 0.5 1 1.5 2

Te

nsil

e s

tress

(M

Pa)

Extension (%)

Upper limit

Lower limit

Mean curve

development of novel 3d woven reinforcements for high...

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