46

CHAPTER 3

MATERIALS AND METHODS

3.1 INTRODUCTION

The main objective of this research work was to produce CFF and

its hybrid fibre reinforced polypropylene composite. In order to achieve this

objective, initially the CFF was characterized for its properties and later the

fibres were mixed / blended and passed through the carding machine to

produce web. These webs were stacked and placed in the compression

moulding machine.

Characterization techniques, namely Physical properties, Chemical

properties and Morphological properties were analyzed for CFF. Thermo

gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC),

Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), fibre density

assessment, thermal analysis, amino acid content and single fibre tensile

testing were used to explain the properties of CFFs. SEM provided a means of

examination of the surface morphology of CFFs. XRD was used to show the

crystallinity of fibre. The fibre density assessment was used to know the

density of the fibre. Thermal analysis was used to obtain information about

the thermal stability of the fibre. Single fibre tensile testing was used to obtain

the tensile properties of fibre. The details of the materials, methods used and

the experimental procedures adopted in the study are described in this chapter.

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3.2 MATERIALS

3.2.1 CFF

The picture of chicken feather is shown in Figure 3.1. Feathers are

highly ordered, hierarchical branched structures, ranking among the most

complex of keratin structures found in vertebrates (Yu et al 2002).

Figure 3.1 Picture of Chicken Feather

The chicken feathers were bought from M/s Suguna Poultry

Industry, Tamilnadu, India. To reduce the variability of feather fibre the

feathers were collected from the broiler chickens grown at the same condition.

Chicken feathers directly collected from a poultry industry are always dirty

and contain various foreign materials, such as skin, blood and flesh, which

need washing by soap. The untreated feathers contain many kinds of bacteria

such as aerobic, anaerobic and enteric. If they grow on the feathers, they will

attack the feather keratin and make it very weak. Finally it decomposes the

chicken feather. Therefore, before using CFF, it is necessary to sterilize it to

inhibit bacteria.

The untreated chicken feathers were washed with 5% soap solution

followed by rinsing to remove its blood stains. The wet washed chicken

feathers were dried in a home dryer with moderate heat. Sterilization

treatment was selected as per the previous findings of Xiuling Fan (2008), he

48

suggested that even though 5% household bleach treatment was the best, the

feathers were turned into yellow after storage for some time indicating

degradation which was not good for later use. Therefore sterilization was

done with 95% ethanol, then rinsed with water and air-dried. Barbs (CFFs)

were manually cut with the help of surgical blade from the quill of the

feathers. To maintain the uniformity of the fiber length the tip , the base of the

feathers was cut and removed. The obtained CFF length varied between 25 to

34 mm, strength was 23.9 g/Tex, moisture regain 12%, breaking extension 1

to 6% and a density of 1.12 g/cc.

3.2.2 Jute Fibre

The long staple jute fibre was supplied by M/s Jothi Jute Textiles

industry, Tamilnadu, India and then it was cut into the fibre length of 30mm

in order to maintain the compatibility of length as in the case of CFF. The jute

fibre strength was 36 g/Tex, moisture regain 13.5%, breaking extension 1.6%

and a density of 1.48 g/cc. As per the investigation on the thermal properties

from DSC by Basak et al (1993), the jute fibre exhibits a moisture desorption

endothermic peak below 1000C and two exothermic peaks at 360 and 474oC.

The first peak corresponds to oxidative degradation and the second to

oxidation of carbon residue and decomposition of lignin (Nguyen et al 1981).

3.2.3 Polypropylene Fibre

The polypropylene staple fibre APOLON® was supplied by Zenith

Fibres Ltd., Baroda, India. The polypropylene fibre length is 51mm, denier

2.5, tenacity 6 g/denier and a density of 0.91 g/cc.

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Figure 3.2 DSC spectra of bulk polypropylene sample as received

DSC tests were performed on the bulk polypropylene sample to

determine the appropriate melting temperature (Tm). DSC curves of the

polypropylene fibres and their Tm obtained is shown in Figure 3.2. The latent

heat of melting for the bulk sample was 100.142 J/g with a Tm peak at

160.43oC.

3.3 METHODS

3.3.1 Properties of CFF

3.3.1.1 Fibre Length

The length of the feather fibre was determined by “Oiled plate

method”. The standard adopted for this test was ASTM D5103-07. This was

an individual-fibre method that was used to measure the length distribution of

short staple fibres. The measurement of individual fibres makes this method

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the most accurate than any other in existence. In this method, a sheet of glass

was smeared with liquid paraffin, and some fibres were placed on the far-left

corner of the glass sheet. Then, the fibres were drawn out one at a time by the

tips of the little fingers of each hand of the operator. The fibres are

straightened and smoothed out over a centimeter scale that had been etched on

the underside of the glass sheet.

The paraffin served to prevent the fibres from being blown away

and assisted in keeping the fibres flat and straight for measurement. The

length of each individual fibre is noted.

3.3.1.2 Fibre fineness

Fineness of feather fibres is tested by air flow method. This is an

indirect method of measuring fibre fineness which is based on the fact that the

airflow at a given pressure difference through a uniformly distributed known

mass of fibres is determined by the total surface area of the fibres and defined

in terms of Microns. The test was carried out as directed in ASTM D 1448.

3.3.1.3 Tensile properties

Feather fibres were mounted on an Instron tensile testing machine

to measure the tensile properties. A gauge length of 1 inch and speed of 15

mm/min was used for testing the CFF. The test was carried out as directed in

ASTM D3822.

3.3.1.4 Fibre moisture content and regain

Conditioning oven was used to determine the moisture content and

moisture regain of the fibre. Two grams of fibre sample was taken and placed

in the chamber. CFFs were first dried in a hot air oven at 135oC for 2 h, the

material weighed and the reading noted. It was again switched on and after

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heating for 30 min the material was weighed. This was carried out till

consistency in weight was observed. The dried samples were allowed to regain

moisture under the standard testing conditions of 21oC and 65% RH. The ratio

of the dry weight of the CFF to the conditioned weight was taken as the %

moisture regain. The test was carried out as directed in ASTM D1576-90.

3.3.1.5 Fibre density

The fibre density was found with a density gradient column having

a blend of carbon tetrachloride (1.592 g/cc) and xylene (0.866 g/cc). The

density of the column will be kept increasing linearly from top to bottom. A

sample placed within the column comes to rest at that position which

corresponds to its own density.

3.3.1.6 Burning characteristics

Standard testing method that is a tuft of the sample CFF was

subjected to burning in a flame. The burning behavior, the odor and the type

and nature of the ash were noted to know the burning characteristics of the

CFF.

3.3.1.7 Morphological structure

A Scanning Electron Microscope (SEM) was used to study the

longitudinal and cross sectional structure of the CFF respectively. Barbs were

mounted on a conductive adhesive tape and sputter coated with gold

palladium prior to observation in the SEM by using JEOL JSM 5400 high

resolution. The applied voltage spot size is 2.0 Kv.

52

3.3.1.8 Thermo gravimetric analysis (TGA)

Thermo gravimetric Analysis or TGA is a type of testing that is

performed on samples to determine changes in weight in relation to change in

temperature. Such analysis relies on a high degree of precision in three

measurements: weight, temperature, and temperature change. The rate of

heating, sample weight, mode of heating and temperature range used for this

study are 10oC, 10 mg, Nitrogen and 1000oC respectively. The TGA tests

were conducted according to ASTM E1131.

3.3.1.9 Differential scanning calorimetry (DSC)

DSC is a technique used to study the thermal transitions of a

polymer. In most DSC design, two pans sit on a pair of identically positioned

platforms connected to a heating source by a common heat flow path. One

pan holds the sample of interest while the other pan is left empty as a

reference. The rate of heating, sample weight, mode of heating and

temperature range used for this study are 10oC, 10 mg, Nitrogen and 550oC

respectively. The melting temperature (Tm) of a sample can be observed by a

peak in the endothermic direction.

3.3.1.10 X-ray Diffraction Studies (XRD)

A Bruker D8 Discover model diffractometer equipped with, a

diffracted beam monochromator, and a copper target X-ray tube set to 40 kV

and 30 mA used for the X-ray diffraction studies. Samples were mounted on a

specially designed sample holder so that the X-ray beam was perpendicular to

the sample. The CFF and wool were powdered in a Wiley mill to about 250

lm in size and made into pellets. The pellets were used to obtain X-ray

diffraction patterns from the Rigaku diffractometer and the diffractograms

were analyzed for % crystallinity.

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3.3.2 Analysis of Samples for Amino acids by High Performance

Thin Layer Chromatography (HPTLC)

3.3.2.1 Sample digestion

The given CFF samples each 250mg were weighed accurately in an

electronic balance and transferred into labeled glass test tubes (BOROSIL).

3ml of 6M Hydrochloric acid solution was added with sample in specified test

tubes. All the sealed tubes were kept in a hot-air oven at 115oC for 48hrs

continuously.

3.3.2.2 Test solution preparation

After completion of sample digestion, the tubes were broken at the

top and the digest transferred into glass beaker (BOROSIL), the tubes rinsed 5

times with distilled water. The acid in the digest was evaporated to core dry

under vacuum using Roto-vac evaporator. The residual content was dissolved

with distilled water and made-up to 6ml in a centrifuge tube. This solution

contained 41.6µg dried raw sample in 1ml distilled water and used as test

solution for amino-acid profile analysis by HPTLC technique. The grouping

of amino acids is shown in Table 3.1

Table 3.1 Grouping of amino acids

Group I Group II Group III Group IV

Asparagine Aspartic acid Lysine Histidine

Glutamine Glycine Glutamic acid Arginine

Serine Alanine Threonine Cystine

Proline Valine Tyrosine Tryptophan

Methionine Phenyl alanine Isoleucine Leucine

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3.3.3 Manufacturing of Composite Boards

The designation, composition and fibre volume fractions (Vf) % of

the composites prepared for this study, is listed in the Table 3.2. The

composite samples were prepared with five different loading of CFF and jute

fibres (50 wt %, 37.50 wt %, 25 wt % and 12.50 wt %). This was done while

keeping the polypropylene content at a fixed loading (i.e. 50 wt %). The

samples have been prepared by varying the process conditions.

The fabrication and properties of fibre composites are robustly

inclined to the proportions of the matrix and the fibre. The proportions can be

expressed either by means of the weight fraction, which is relevant to

fabrication, or by the volume fraction, which is commonly used in property

calculations.

Table 3.2 Formulation of Composites and Fibre volume fraction (Vf)

Designation of Samples

Composition (Vf) %

Reinforcement Matrix

100% CFF CFF (50 wt %) + Polypropylene (50 wt %) 40.54 59.46

75:25 CFF/Jute

CFF (37.50 wt %) + Jute (12.50 wt %) + Polypropylene (50 wt %)

42.1 57.9

50:50 CFF/Jute

CFF (25 wt %) + Jute (25wt %) +

Polypropylene (50 wt %) 39.25 60.75

25:75 CFF/Jute

CFF (12.50 wt %) + Jute (37.50 wt %) + Polypropylene (50 wt %)

40.72 59.28

100% Jute Jute (50 wt %) + Polypropylene (50 wt %) 37.82 62.18

After the mixing of fibres (CFF, jute and polypropylene), these were fed into

miniature carding machine, as shown in Figure 3.3, for four times to ensure

the homogenous blending and finally the webs were produced. The webs were

conditioned at 115oC for 24 hours to remove any moisture present in it. The

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technical specifications of miniature carding machine (Trytex) are given in

Table 3.3.

Figure 3.3 Miniature Carding machine

Table 3.3 Technical specification of miniature carding machine

Particulars Licker-in Cylinder Doffer

Diameter (inch) 5 10 7

Wire Points (per square inch) 04 860 403

Wire type and angle ICC 400

and 4oICC 550

and 30oICC 600

and 30o

Speed (rpm) 1000 350 10

Composite boards were produced from carded web by using

compression moulding technique as shown in Figure 3.4. Fibrous webs were

cut into pieces and placed on the mould. The webs were stacked to get the

required weight/unit area (1000 grams per square meter). The platens were

pressed to desired specific pressure and temperature for pre-defined time to

get moulded product. The widely used thermocouples temperature sensor was

used to measure and confirm the temperature inside the stack as per the

chosen values during processing of composite manufacturing. After

completion of compression cycle, the platens were cooled to optimum

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temperature and then the pressure was released to take out the board. The

technical specification of compression moulding machine is given in Table

3.4. Several of such fibre webs were compression moulded by varying the

process conditions such as temperature, pressure and time.

Figure 3.4 Compression Moulding (Hot pressing) machine

Table 3.4 Technical Specifications of Compression Moulding Machine

Particulars Specifications Maximum capacity 20 Tons Make and Type REDO and 4 Pillars & Plates Acting Single acting Movement Upward stroke Platen size 300 X 300 mm No of day light SingleDay light gap 150 mm Stroke length 150 mm Piston diameter 120 mm No of heaters 3 Nos., 500 watts in each plate Maximum temperature 300o C Temperature accuracy +/- 5oCHeaters Cartridge type Electrical Heater (dia 25 mm) Heater Controls Digital temperature Controllers “J” type Timer Digital type Oil tank capacity 15 liters Maximum Operating Pressure 500 bar

57

3.3.3.1 Fibre volume fraction

The fibre volume fraction of a composite material may be

determined by chemical matrix digestion, in which the matrix is dissolved and

the fibres weighed and calculated from substituent weights and densities by

using the equation shown in 3.1. The average fibre volume fraction was

obtained based on 5 specimens for each fibre composite.

fmmf

fmf WW

WV (3.1)

where Vf = volume fraction of fibres

Wf = weight of fibres

Wm = weight of matrix

f = density of fibres

m = density of matrix

3.3.4 Mechanical and Water Absorption Testing

Tensile, Impact, flexural and water absorption tests were

conducted. All the samples were conditioned as per the standards (room

temperature 23oC, relative humidity of 62%) before testing. For each test and

type of composite, seven specimens were tested and at least five imitate

specimens were presented as an average of tested specimens.

3.3.4.1 Tensile strength test

All tensile testing specimens were cut into dog-bone shape. The

tensile tests were conducted by using INSTRON (Model 4301) Universal

Testing Machine with load cell of 1 Kilo Newton, using a crosshead speed of

50 mm/min. Tests were performed until tensile failure occurred. The

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dimensions of the specimens for tensiletesting were 250 x 25 x 4 mm (length

x width x thickness). The unit of tensile strength is noted in Newton.

3.3.4.2 Impact strength test

The test was performed based on the ASTM D6110 in the charpy

impact strength tester. Charpy impact tests were conducted on notched

samples. Before the test sample was mounted on the machine, the pendulum

was released to calibrate the machine. The test samples were then gripped

horizontally in a vice and the force required to break the bar was released

from the freely swinging pendulum. The value of the angle through which the

pendulum had swung before the test sample was broken corresponding with

the value of the energy absorbed in breaking the sample and this was read

from the calibrated scale on the machine. The unit of Impact strength is noted

in Joules.

3.3.4.3 Flexural strength test

Flexural testing determines the strength of materials when a force is

applied perpendicular to the longitudinal axis of sample. Flexural test (a three

point bending) was carried out on the same Instron machine (Model 4301)

according to the ASTM D790. The unit of flexural strength is noted in

Newton.

3.3.4.4 Water absorption test

In order to measure the water absorption characteristics of the

composites, rectangular specimens were prepared having dimensions of 30 x

10 x 5 mm. The specimens were dried in an oven at 115oC, cooled in

desiccators and immediately weighed. High precision electronic weighing

balance was used for weight measurement. The dried and weighed specimens

59

were immersed in hot distilled water according to ASTM D 570-99 for 2

hours. As the jute fibers are hygroscopic, water diffusion behavior of the

composites is expected to depend on the fiber content. After immersion, the

excess water on the surface of the specimens was removed using a soft cloth.

The final weight of the specimens was then taken. The increase in the weight

of the specimens was calculated using the equation:

100%WeightOriginal

WeightOriginalWeightFinalAbsorptionWater (3.2)

3.3.4.5 Fracture surface of composite by using scanning electron

microscope (SEM) analysis

The morphology and microscopy of composite samples were

studied by using JEOL JSM 5400 high resolution SEM micrograph. Prior to

the analysis, the specimens were placed on a stub and were coated with thin

layer of gold using sputter coater to avoid charging under the electron beam.

The results are presented in the appropriate chapters.

3.3.5 Acoustic testing

Measurement techniques used to characterize the sound absorptive

properties of a material as observed by Takahashi et al (2005) are:

Reverberant Field Methods

Impedance Tube Methods

Steady State Methods

All the composite samples of this work were tested by using the

two microphone impedance tube method (ASTM E 1050), which is described

below in section Impedance Tube Method. This method uses plane sound

waves that strike the material straight and hence the sound absorption

60

coefficient is called normal incidence noise absorption coefficient, (NAC).

This research uses impedance tube method which is faster and generally

reproducible and, in particular, requires relatively small circular samples,

either 35 or 100 mm in diameter (according to the type of impedance tube). In

the impedance tube method, sound waves are confined within the tube and

thus the size of the sample required for test needs only be large enough to fill

the cross-section of the tube (Kin Ming Ho et al 2005). Thus this method

avoids the need to fabricate large test sample with lateral dimensions several

times the acoustical wavelength.

3.3.5.1 Impedance tube method

Two-fixed microphone impedance tube or transfer function method

(ASTM E 1050), is relatively a recent development. In this technique, a

broadband random signal is used as a sound source. The normal incidence

absorption coefficients and the impedance ratios of the test materials can be

measured much faster and easier compared with the first technique (Dieter

et al 2002). The transfer function method (ASTM E 1050) covers the use of

an impedance tube, with two microphone locations and a digital frequency

analysis system for the determination of normal incidence sound absorption

coefficients and normal specific acoustic impedance ratios of materials.

The sound absorption coefficient, , of a material is the fraction of

incident sound energy the surface absorbs or otherwise it does not reflect. The

noise reduction coefficient, (NRC), is a single number, which is the average

value of the material’s absorption coefficients at frequencies of 250, 500,

1000 and 2000 Hz, expressed to the nearest 0.05 integers (Harris 1979). This

value is used to select or specify materials in noise control applications. If

higher the NRC value, greater the average sound absorption. Where low or

very high frequencies are involved, however, it is usually better to compare

absorption coefficients instead of noise reduction coefficients.

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3.3.6 Design of Experiment

Response surface methodology is an experimental modelization

technique dedicated to the evaluation of the connection of a set of controlled

experimental factors and observed results. It requires prior facts of the process

to achieve statistical model. A detailed account of this technique has been

outlined (Box and Behnken 1960).

Basically this optimization process involves three major steps,

performing the statistically designed experiments, estimating the coefficients

in a mathematical model, and predicting the response and checking the

competence of the model. The significant variables used in the present

research like temperature, pressure and time were chosen as the critical

variables and selected as x1, x2 and x3 respectively. The low, middle, and high

levels of each variable were designated as -1, 0, and +1 respectively, and

given in Table 3.5. The actual design of experiments is given in Table 3.6.

Computation was carried out using multiple regression analysis using the least

squares method.

In a system involving three significant independent variables

x1, x2, x3 the mathematical relationship of the reaction on these variables can

be approximated by the quadratic (second degree) polynomial equation as

shown in Equation 3.3.

Y = C0 + C1x1 + C2x2 + C3x3 + C12x1x2 + C13x1x3 +

C23x2x3 + C11x12 + C22x22+C33x32 (3.3)

where Y = predicted yield,

C0 = Constant,

C1, C2 and C3 = linear Coefficients,

C12, C13 and C23 = cross product Coefficients

C11, C22 and C33 = quadratic Coefficients

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Table 3.5 Levels of variables chosen for the research

VariableCoded level

-1 0 +1

Temperature (oC) 165 175 185

Pressure (Bar) 5 10 15

Time (Minutes) 3 6 9

The levels of variables like temperature, pressure and time were

chosen based on the melting point of the resin used, final thickness (minimum

of 5 mm) expected in the composite board and the effect of thermal exposure

period respectively. A multiple regression analysis was done to obtain the

coefficients and the equation can be used to predict the response. The degree

of experiments chosen for this study was Box-Behnken, a fractional factorial

design for three independent variables. It is applicable once the critical

variables have been identified (Box and Behnken 1960).

In the model given in Equation (3.3), interactions higher than first

order have been neglected. The design is preferred because relatively few

experimental combinations of the variables are adequate to estimate

potentially complex response functions (Annadurai and Sheeja 1998). A total

of 15 experiments were necessary to estimate the 10 coefficients of the model

using multiple linear regression analysis, the set of coefficients for its

mechanical properties and acoustic property was calculated.

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Table 3.6 Box-Behnken design for the three independent variables

Runorder

Levels of variables

x1 Level x2 Level x3 Level

Coded Actual Coded Actual Coded Actual

1 1 185 -1 5 0 6

2 0 175 1 15 -1 3

3 0 175 0 10 0 6

4 0 175 1 15 1 9

5 -1 165 0 10 1 9

6 0 175 0 10 0 6

7 -1 165 0 10 -1 3

8 1 185 1 15 0 6

9 1 185 0 10 -1 3

10 -1 165 -1 5 0 6

11 0 175 0 10 0 6

12 0 175 -1 5 -1 3

13 1 185 0 10 1 9

14 -1 165 1 15 0 6

15 0 175 -1 5 1 9

3.3.7 Statistical Analysis

3.3.7.1 ANOVA

In order find the relative contribution of process conditions on

mechanical properties (tensile, impact and flexural strength) and acoustic

properties of the manufactured composites; ANOVA was performed on

experimental data at 95% confidence level which shows F observed vs. F

critical. The P-value was set at 0.05.

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3.3.7.2 Response optimization

With the help of Minitab 15 software the response optimization was

found out. In Minitab the response optimizer searches for a combination of

input variables that jointly optimize a set of responses by satisfying the

requirements for each response in the set. The optimization was accomplished

by the following criteria:

1. Obtaining the individual desirability (d) for each response.

2. Combining the individual desirable to obtain the combined or

composite desirability (D).

3. Maximizing the composite desirability and identifying the

optimal input variable settings.

To maximize the composite desirability, Minitab employs a

reduced gradient algorithm with multiple starting points that maximize the

composite desirability to determine the numerical optimal solution.

3.3.8 Experimental Approach

Composites were prepared at different processing conditions to

study the effect of the process variables on mechanical properties like tensile,

impact and flexural strength. A lower temperature was not chosen since the

melting temperature of Polypropylene core is 160oC which can be supported

by the DSC graph of polypropylene in Figure 3.3. A higher temperature was

avoided due to possible partial degradation of CFF at 186oC understood

through a gentle but distinct burning odor, which can be supported as per the

discussion in chapter 4. So, to make a composite board, the temperature has

been chosen between 165 to 185oC. In order to study the acoustic properties,

samples from composites with 100% CFF, 75: 50% and 25% CFF and Jute

fibre have been used. The work flow chart is shown in Figure 3.5.

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Figure 3.5 Work Flow Chart

Collection of Chicken feathers

Blending of reinforced fibres and matrix with different fibre loadingReinforcement +Matrix

(50, 37.50, 25, 12.50 wt %) + (50 wt % constant)

Purification of Chicken feathers (Hot water, Ethanol)

Separation of CFF from quills (Using surgical blades)

Characterization of CFF (Physical, Chemical, Thermal and Structural Properties)

Composite manufacturing (Compression moulding) with different processing conditions (Temperature – 165,175,185oC), (Pressure –

5, 10, 15 Bar) and (Time – 3, 6, 9 Minutes)

Testing of Composites Mechanical Properties (Tensile, Impact and Flexural Strength)

Testing of Composites Acoustic Properties (Impedance Tube Method)