Tribological behaviour of natural fiber (luffa cylindrical)

reinforced hybrid epoxy composite

Dr S K Acharya,Professor

&

Niharika Mohanta (research scholar)

Department of Mechanical Engineering, N I T Rourkela -769008 Orissa,

India

ABSTRACT

Environmental awareness today is motivating the researchers worldwide on the

studies of natural fibre reinforced polymer composite as cost effective option to synthetic

fibre. The easy availability of natural fibres and manufacturing process have tempted

researchers to try locally available inexpensive fibres and to study their feasibility of

reinforcement purposes and to what extent they satisfy the required specifications of good

reinforced polymer composite for tribological applications. With this background in this

present work the effect of stacking sequence on erosive wear behaviour of untreated luffa

cylindrica fibre and glass fabric reinforced epoxy hybrid composites has been investigated

experimentally. Composite laminates were fabricated by hand lay-up technique. All the

composites were made with a total of 4 plies, by varying the number and position of glass

layers so as to obtain five different stacking sequences. The erosion rates of these composites

have been evaluated at different impingement angles (30º,45º,60°,90°) and at four different

particle speeds (v=48, 70, 82,109 m/s). Silica sand with size 200-250 μm of irregular shapes

is used as erodent. The impingement angle was found to have a significant influence on the

erosion rate. The composite laminate showed semi ductile behaviour with maximum erosion

at 45-600 impingement angles. The Factograpic analysis of the eroded surface was examined

by SEM. From the study it is concluded that the erosive wear behaviour of natural fibre luffa-

cylindrica can be improved significantly by hybridizing with synthetic fibre glass.

Key Word: Natural fiber, Hybrid composite, Erosive wear, Semi ductile,SEM

Tribological Behavior of natural fiber( luffa cylindrical)

reinforced epoxy composite

Dr S. K. Acharya

Department of Mechanical Engineering

National Institute of Technology

Rourkela

Presented by

Introduction

Objectives Present Work

Results and Discussion

Conclusion

References

CONTENTS

Composite materials – Introduction

A composite material consists of two or more combined constituents that are combined with a macroscopic level and are in not soluble each other.

Reinforcement phase (e.g., Fibers) Binder phase (e.g., matrix)

Reinforcement + Matrix = Composite

Mud/Straw Bricks Concrete Fiberglass

CLASSIFICATION OF COMPOSITES

1. Based on the type of matrix phase

• Metal Matrix composites (MMCs)

• Ceramic Matrix composites (CMCs)

• Polymer Matrix Composites (PMCs)

2. Based on the type of reinforcement

• Fiber Reinforced composites.

• Particle Reinforced (particulate)

composites.

• Laminate Composites

Fibers used for structural applications:

• Glass fiber.

• Kevlar fiber (Aramide).

• Carbon and graphite fiber.

• Boron fiber.

• Organic fibers.

• Fibers from natural sources.

5

Natural Fibers

Bottlenecks

Advantages of Natural fiber Reinforcement

1. Environmental reasons: Renewable resource of raw material Thermally recyclable, biodegradable, Low energy consumption

2. Excellent specific strength & high modulus 3. Health & safety: less abrasive, safe manufacturing processes 4. Lower cost & reduced density of products

1. Variability 2. Hydro-philicity (moisture)3. Weak interface

Why Bio-Fiber Composites ?

Department of Mechanical Engineering, NIT Rourkela

Background and Objective of

the Present Work

It is known that natural fibre composite posses much lower mechanical

strength properties than synthetic fibre reinforced composite. Hence

the use of natural fibre alone in polymer composite is inadequate in

satisfactorily tackling all the technical needs of a fibre reinforced

composite. It is reported that if natural fibre is hybridised with a

synthetic fibre in the same matrix the properties of natural fibre could

be improved by taking the advantage of both the fibres.

In this present work the effect of stacking sequence on erosive wear

behaviour of untreated luffa cylindrica fibre and glass fabric reinforced

epoxy hybrid composites has been investigated experimentally.

Composite laminates were fabricated by hand lay-up technique. All the

composites were made with a total of 4 plies, by varying the number and

position of glass layers so as to obtain five different stacking sequences.

Thursday, February 12, 2015 10

The plant with fruit luffa cylindrica

Dried luffa cylindrica

Luffa cylindrica commonly called sponge

gourd, loofa, vegetable sponge, bath sponge

or dish cloth gourd.

It belongs to cucurbitaceous family . Luffa cylindrica is a sub-tropical plant, which

requires warm summer temperatures and

long frost-free growing season when grown in temperate regions.

They have a long history of cultivation in the

tropical countries of Asia and Africa.

The main commercial production countries

are China, Korea, India, Japan and Central America .

Luffa cylindrica

11

Luffa cylindrica Cont…

The outer core open as natural mat

Sponge guard with hollow micro channels

The LC strut are characterized by a micro cellular architecture with continuous hollow microchanels which forms a vascular bundles and yield a multimodal hierarchical pore system.

Luffa cylindrica form a natural mat that deviates the crack path, leading to a controlled fracture mode of a composite and increasing the composite’s toughness.

The fruit luffa cylindrica has a fibrous vascular system that forms a natural mat when dried.

Some of the use of Luffa cylindrica fiber

Bathroom sponge

Component of shock absorbers

Sound proof linings

Utensils cleaning sponge

Packing materials

Making crafts

Filters in factories

Part of soles of shoes

Decorative items

12

Luffa cylindrica

13

ITEM cellulose

(wt%)

Hemicellulos

es

(wt%)

Lignin

(Wt%)

sisal 60-75.2 10.0-16.5 7.6-12.0

Ramie 68.6-85.0 3.0-13.1 0.5-0.6

Cotton 82.7-90.0 5.7-6.0 -

Hard wood 40.0-45.0 32.0-33.0 17.0-26.0

Luffa cylindrica 60-63 19.4-22 10.6-11.2

Cont…

Chemical composition of some lignocelluloses source (Satyanarayana et al 2007)

The main chemical constituents of natural fiber are –

cellulose

- hemicelluloses

- Lignin

Hemicelluloses and cellulose are present in the form of

holocellulose , which contribute to more than 50% of the total

chemical constituent present in the fiber

Lignin - rigidity of the fibers

- high molecular weight

- three dimensional polymer structure

- acts as a binder for the cellulose fibers

- behaves as an energy storage system

Cellulose - high tensile strength of composite materials.

Carbon content in fiber provides

- light weight

- high strength and

- favorable stiffness

Chemical composition of plant fibre

WEAR

Wear is the loss of material from one or both of the contacting

surface when subjected to relative motion.

WEAR

Adhesive Abrasive Fatigue Fretting Erosion

Department of Mechanical Engineering, NIT Rourkela

Department of Mechanical Engineering, NIT Rourkela

Erosion

Wear due to mechanical interaction between the surface and a

fluid, a multi-component fluid, or impinging liquid or solid

particles.

Erosion is caused by a gas or a liquid which may or may not

carry solid particles, impinging on a surface. When the angle of

impingement is small, the wear produced is closely analogous to

abrasion. When the angle of impingement is normal to the

surface, material is displaced by plastic flow or is dislodged by

brittle failure.

Department of Mechanical Engineering, NIT Rourkela

Erosive Wear Due to Solid Particle Impingement Applications adversely affected by erosion

Polymer processing machines and others

Coal plants (transport of pulverized coal)

Gas turbines

Power plants

Pipelines

Ship propellers

Aircraft

• Windshield • Wings • Propellers • Rotors

Department of Mechanical Engineering, NIT Rourkela

VARIABLES AFFECTING PURE EROSION 1. IMPINGEMENT VARIABLES

• Particle velocity

• Angle of incidence

• Flux (particle concentration)

2. PARTICLE VARIABLES

• Particle shape

• Particle size

3. MATERIAL VARIABLES

• Hardness

• Work hardening behavior

19

The dried luffa cylindrica fruit was collected

locally.

The bark and seeds were removed, and the

fibrous fruit was washed thoroughly with

distilled water until the colour of the water

used in this procedure was colourless.

LC Fibre were dried in an woven for 6 h at

70°C and stored in a desiccators with silica

gel.

LC fibers were cut to rectangular mat like as

shown in figure from the sponge guard

neglecting the end portion to keep the

thickness same for the mat .

Fiber preparation

Department of Mechanical Engineering, NIT Rourkela

Ingredients used for composite Preparation: - Fiber:- luffa cylindrica fiber, glass fiber Polymer:- Araldite LY 556 (CIBA GEIGY Ltd.) Hardener :- HY951

Mould used for casting:-

A wooden mold (dimension 140×60×6 mm) was used

for casting the composite slab

Method : Hand lay-up technique.

Preparation of the composite

Luffa Cylindrica Fibre

Glass Fibre

Preparation of the composite

Department of Mechanical Engineering, NIT Rourkela

Symbol

Laminate

stacking

sequence

Total Fibre

Thickness

(mm) Weight fraction

(%)

Volume fraction

(%)

S1 LLLL 18.52 30.86 5.6

S2 LGLG 24.42 28.99 5.12

S3 LGGL 17.72 19.12 5.12

S4 GLLG 18.50 19.87 5.13

S5 GGGG 14.27 6.7 5.00

L-Luffa cylindrica layer , G-Glass fibres layer

Table . Laminate stacking sequence

Test for Erosive wear

Details of erosion test rig. (1) Sand hopper. (2) Conveyor belt system for sand flow. (3) Pressure transducer. (4) Particle-air mixing chamber. (5) Nozzle. (6) X–Y and h

axes assembly. (7) Sample holder

Air Jet Erosion Test Rig :

ASTM G76

Erodent Silica sand

Erodent size (µm) 200±50

Erodent shape irregular

Impact angle 30°,45°,60°,90°

Impingement velocity (m/s) 48,70,82,109

Erodent flux rate (g/min) 3

Test temp Room temp

Standoff distance (SOD) (mm)

10

Test parameter

e

rw

wE

Weight loss of the sample has bee taken in a interval of time of 3 min.

The erosion rate (Er) is then calculated by using the following equation: -

Where:-

Δw= mass loss of test sample in gm . We= mass of eroding particles (i.e., testing time × particle feed rate).

The erosion efficiency (η) can be obtained by the following equation as proposed by Sundararajan et al. :-

2

2

v

HEr

Where: -

Er = Erosion rate (g/g)

H = Hardness of eroding material (Pa)

V= Velocity of impact (m/s).

The theoretical density of composites is obtained as per the following equation:

The actual density (ρce) of the composite, is determined experimentally by simple water-immersion technique.

Stacking

sequence

Theoretical

density

(g/cm3)

Measured

density

(g/cm3)

Volume fraction

of voids (%)

Neat

epoxy

1.2 1.18 1.66

S1 1.01 1.009 1.2

S2 1.18 1.178 .89

S3 1.187 1.177 .878

S4 1.188 1.179 .78

S5 1.305 1.297 .65

Measured and theoretical densities of the composites.

Influence of impingement angle (α) on erosion wear behavior

(a) (b)

FIG. Erosion rate as a function of impingement angle for different laminate stacking sequence at impact velocity (a) 70 m/s d) 109 m/s.

From the experimental results it is clear that the developed hybrid composites

respond to solid particle impact neither behaves in a purely ductile nor in a brittle

manners. Since maximum erosion occurs in the range of 45°-60°impact angles for

all impact velocities. Therefore it can be concluded that luffa cylindrica-glass fiber

reinforced epoxy hybrid composites behaves in a as semi- ductile nature.

Influence of impact velocity on erosion wear behavior

FIG. Variation of steady-state erosion rate of luffa cylindrica-glass reinforced epoxy hybrid composite as a function of impact velocity (48–109 m/s) at (a) Impingement angle 45° (b) impingement angle 60°.

(a) (b)

steady-state erosion rate all laminate stacking sequences for different impingement angles increases with increase in impact velocity.

The velocity of erosive particle has a very strong effect on erosion rate. It was found that the erosion rate follows power low behaviour with particle velocity, E= kVn where E, is the steady-state erosion rate, v the impact velocity of particles, n the velocity exponent and k is a constant.

The velocity exponents n for the various laminate sequences at different impingement angles were found in the range of 1.5533–2.9943

Erosion efficiency

Fig. Erosion efficiency as a function of impact velocity for luffa cylindrica-glass reinforced epoxy hybrid composite (a) Impingement angle 60° (b) impingement angle 90 °

The erosion efficiencies of composite laminates vary from 1.24 to 4.24% for different impact velocities studied at 600 impact angles and it vary from 0.80 to 3.55% for 900 impact angle. Hence, in present study it is established that erosive wear takes place due to micro ploughing and micro cutting.

The laminate stacking sequence S4 shows lower erosion efficiency among all hybrid laminate at different impact velocities indicate a better erosion resistance.

(b) (a)

Formation of

crater

Formation of crater

Breakage of

fibres

Surface morphology of eroded surface

Fig.SEM micrographs of eroded surface at impingement angle 60° and at impact

velocity 82 m/s for laminate stacking

sequences (a) S1 (b) S2

(b) (d)

Figure (a) & (b) shows the SEM

micrograph of the composite laminate

for stacking sequence S1 and S2 at 60º

impingements angle for impact

velocity 82 m/s.

Pulling out of fibers from the matrix

is not visible. At some places craters

are being formed due to penetration of

silica sand which causes damage to

the matrix material.

S1

S2

Formation of smooth surface

Breakage of

fibres

Fig.SEM micrographs of eroded surface at impingement angle 60° and at impact

velocity 82 m/s for laminate stacking

sequences (a) S3 (b) S4

Fig (c) shows the damage caused to the

fibres for the sequence S3.The meshing to

the originally structure is totally damaged

and smooth surfaces are being formed.

Fig (d) shows the surface damage caused

to sequence S4.Breaking of glass fibres in

the micrograph are found but there is no

chipping up fibres from the matrix is found.

Damage to the luffa fibre is totally eliminated

because of position of glass fibre at the

outer layer

(c)

(d)

S3

S4

Breaking of glass fibres

Formation of

cavity Damage

of fibre

surfaces

FIG. SEM micrographs of eroded surface at impingement angle 60° and impact velocity

109 m/s for laminate stacking sequences (a)S3

(b) S4

(e)

(b)

For sequences S3 after eroding the

luffa fiber surface the erodent particles

enters to the glass fiber surface.

Breaking of glass fires is seen but

chipping out of fibres from the matrix is

prevented. This might be due to a good

bonding between the fibres and the

matrix and the time it gets erode the

glass fibre is less.

Fig (f) shows the damage caused to

sequence S4 due to higher velocity

(109 m/s).Formation of cavity is clearly

visible which is formed by

microploghing and cutting also

extensive damage caused at this

velocity to the luffa fibre surface is

seen

(f)

S3

S4

The influence of impingement angle on erosive wear of all laminate stacking

sequence under consideration exhibit semi ductile behavior with maximum wear

rate at 45-600 impingement angles.

Erosion rate (Er) different laminate stacking sequences displays power law

behavior with particle velocity (v) as E α vn. The velocity exponents are in the

range of 1.5533–2.9943 for various materials studied for different impingement angles (30°–90°) and impact velocities (48–109 m/s).

Erosion efficiency is found to be in the range of 0.84% to 4.24% for different

laminate stacking sequence at different impact velocity. So material removal is

mainly due to microploughing and micro cutting.

It is clear from this study that erosive strength of natural luffa cylindrica fiber

can be increased by hybridization with synthetic fiber.

The morphologies of the eroded surfaces observed by SEM suggest that overall

erosion damage of the composite is mainly due to breaking of fiber. Fiber pull out

is prevented due to good bonding between the fiber and the matrix.

Conclusion

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