Woven Fabric Composites by Compression and …shodhganga.inflibnet.ac.in/bitstream/10603/7115/20/20...Chapter 9 Woven Fabric Composites by Compression and Resin Transfer Moulding Abstract

Chapter 9

Woven Fabric Composites by Compression and Resin Transfer Moulding

Abstract

This chapter deals with the static and dynamic mechanical

properties of banana and sisal woven fabric reinforced polyester

composites. It consists of two parts; chapter 9.1 and 9.2. Chapter

9.1 presents the static mechanical properties of the composites

prepared by compression and resin transfer moulding. Chapter 9.2

deals with the dynamic mechanical properties of the above

composites. The properties of the composites obtained in the

compression moulding method is compared with to those of resin

transfer moulding.

Chapter 9.1

Mechanical Performance of Banana and Sisal Woven Fabric Reinforced Polyester Composites Fabricated by

Compression and Resin Transfer Moulding Techniques

Abstract

Banana and sisal woven fabric-reinforced polyester composites were

prepared by compression and resin transfer moulding. The mechanical

properties were investigated with respect to fibre volume fraction and

layering patterns of fabric. Both fibres were woven in the same pattern with

minimum amount of fibre in the weft region. Up to three layers of fabrics

were arranged in the parallel way ( ) for moulding. When the specimens

were cut longitudinally (L), along the weave direction, tensile and flexural

properties were found to be higher in the bilayer composites. The tensile

and flexural properties obtained from the composites by the resin transfer

moulding were found to be higher than those of compression moulding. As

the volume fraction increased, the tensile and flexural properties

increased to a particular fibre loading, and then decreased. Impact

strength increases with fibre loading. In all cases, the tensile strength was

found to be higher in banana fabric reinforced polyester composites

compared to sisal. But the impact strength was found to be higher in sisal

fabric composites. When the fabrics are arranged parallel and

perpendicular ( ) in alternate layers, four layer composites could also be

prepared. In this case, the trilayer composite showed maximum tensile

strength, tensile modulus, flexural strength and flexural modulus.

Results in this chapter have been communicated to Journal of Material Science

312 Chapter 9.1

9.1.1. Introduction

A growing interest in textile composites has been observed in recent years.

Woven fabric reinforced composites are the most widely used form of

textile structural reinforcement.1,2 The increased interest in textile

reinforcements is due to several factors like their strength, lower

production cost and improved mechanical properties when compared to

their non-woven counterparts. Moreover, textile structural composites are

associated with near net shape and cost effective manufacturing process.

The process of weaving in which the fabric is formed by interlacing warp

and weft (fill) strands/yarns forms woven fabrics. Lateral cohesion is a

serious problem encountered in the preparation of the reinforcing

elements, but this can be overcome through woven reinforcements.

Twisted yarns have been reported to increase the lateral cohesion of the

filaments as well as facilitate their easier handling.3 By twisting the yarns

the possible micro damages with in the yarn can be localized, leading to a

possible decrease in the failure strength of the yarn. Their use in the

fabrication of structures with high mechanical performance is increasing in

the field of aeronautics, naval construction and automobile engineering.4

Since they provide excellent integrity and conformability for advanced

structural composite applications, woven fabrics are viable and attractive

as reinforcements. The major driving force for the increased use of woven

fabrics, compared to their non-woven counterparts, are excellent

drapeability (allowing complex shapes to be formed), reduced

manufacturing costs (e.g. a single two-dimensional biaxial fabric replaces

two non-woven plies)5 and increased resistance to impact damage

(improved compressive strengths after impact follow from a reduction in

the area of impact damage).6 These woven fabric composite materials

have better out-of-plane stiffness, strength and toughness than laminate

composites. They also have easier handling in production quality.

Mechanical Performance of Banana and Sisal Woven Fabric… 313

Shin and Jang7 reported on the important role in the delamination

resistance of woven fabric composites. Gommers et al.8 investigated the

application of Mori-Tanaka method for the calculation of the elastic

properties of textile composite materials. Bhattacharya et al.9 have made

composites using jute fibres in phenolic resin. They have reported the

effect of processing variables on the mechanical properties of the

composites. Chawla et al.10 as well as Shah and Lakkad11 studied hybrid

composites with glass and jute fibres in resin matrices and found that a

small addition of glass fibres increases the tensile strength and tensile

modulus of jute composites. They have suggested that jute can be used as

a filler fibre in glass fibre composites. Gowda et al.12 have reported on the

use of jute fabric as reinforcement in polyester composites. A

comprehensive study conducted on the mechanical properties of the

above composites has arrived at the conclusion that although the

mechanical properties of jute/polyester composites do not possess

strength and modulus as higher than those of conventional composites,

they do have better strength than wood composites and some of the

plastics. Twisted yarns have been reported to increase lateral cohesion of

the filaments as well as improve the ease of handling.13 In fact, fibre twist

induces normal forces between fibres resulting in an increased inter-fibre

friction yarn cohesion.

Recently, Sapuan et al.14 studied the tensile and flexural properties of

woven banana reinforced epoxy composites. Three samples prepared

from woven banana fibre composites of different geometries were used in

this study. From the results obtained, it was found that the maximum value

of stress in x-direction is 14.14 MN/m2, meanwhile the maximum value of

stress in y-direction is 3.398 MN/m2. For the Young’s modulus, the value of

0.976 GN/m2 in x-direction and 0.863 GN/m2 in y-direction were computed.

314 Chapter 9.1

As in the case of three-point bending (flexural), the maximum load applied

is 36.25 N to get the deflection of woven banana fibre specimen beam of 0.5

mm. The maximum stress and Young’s modulus in x-direction was recorded

to be 26.181 MN/m2 and 2.685 GN/m2, respectively. Statistical analysis

using ANOVA-one way has showed that the differences of results obtained

from those three samples are not significant, as they confirm a very stable

mechanical behaviour of the composites under different tests. This shows

the importance of this product and paves the way for the researchers to

develop an adequate system to produce a good quality woven banana fibre

composite which may be used for household utilities. The mechanical

properties of woven flax fibre reinforced recycled HDPE composites were

studied by Foulk and co-workers.15 Fabrics were treated with maleic

anhydride, silane and enzyme to promote interaction between polymer and

fibres. Compared to recycled HDPE, mechanical properties of composites

materials demonstrated significant increase in tensile strength and modulus

of elasticity. The mechanical properties and fracture surface morphology of

woven date palm fibre (DPF) reinforced polyester resin composites were

investigated by Wazzan.16 Laminates with different orientation and volume

fraction of reinforcement were prepared using resin transfer moulding

(RTM) processing technique. The woven DPF reinforced composites

recorded a tensile strength of 76.9 MPa. Xue and Cao17 developed an

integrated micro- and macro-constitutive model to predict the mechanical

properties of woven composites during large deformation based on the

microstructure of composites, i.e., the dimensions of fibres, yarns and unit

cell, the material properties of composite constituents, as well as the

orientation of yarns. The proposed integrated micro/macro-model denoted

excellent agreement with the experimental data and the 3D finite element

results.


Researchers have studied the micromechanics of moisture diffusion in

woven composites.18 The weave pattern of the fabric denoted a profound

effect on the water uptake of the composites. They observed that woven

composites exhibited quicker diffusion than the unidirectional laminate with

the same overall fibre volume fraction. The quickest diffusion process was

exhibited by the plain weave with a lenticular tow and large waviness. The

effect of fibre surface treatments (silane and permanganate treatments)

on tensile strength and modulus of sisal textile reinforced vinyl-ester resin

composites was investigated by Li et al.19 Chemical modification of fabric

has not been able to make a significant improvement in tensile properties.

Pothen et al.20conducted tensile and impact studies of woven sisal fabric

reinforced polyester composites prepared by RTM technique. It has been

found that the weave architecture is a crucial factor in determining the

response of the composites. The thermal diffusivity, thermal conductivity

and specific heat of jute/cotton, sisal/cotton and ramie/cotton hybrid fabric-

reinforced unsaturated polyester composites were investigated by Alsina et al.21

The thermal properties of the fabrics, i.e. without any resin, were also

evaluated and were used to predict the properties of the composites from

the theoretical series and parallel model equations. The effect of fabric pre-

drying on the thermal properties of the composites was also evaluated.

The results denoted that the drying procedures involved did not bring

about any relevant change in the properties evaluated. Thomas and co-

workers22,23 recently reported the mechanical properties as well as the

moisture sorption characteristics of textile sisal reinforced natural rubber

composites. Sisal fabric was subjected to various chemical treatments.

Tensile strength was seen to decrease with all chemical modifications

except for composites prepared with heat-treated sisal fabric. Water

uptake has been found to be the maximum for textile composites

containing sisal fabric treated with 4% NaOH.

316 Chapter 9.1

The earlier studies conducted by this research team on short fibre

composites revealed that the tensile properties of banana/polyester

composites were higher than that of sisal/polyester composites, while

impact properties, vice versa.24 The properties obtained for the short

banana/sisal hybrid fibre composites fabricated by compression and resin

transfer moulding were compared in the last chapter. However, no work

has been carried out to compare the properties of banana as well sisal

woven fabric composites by the above mentioned methods. In this study

the mechanical properties such as tensile strength, tensile modulus,

flexural strength, flexural modulus and impact strength of woven fabric

composites of banana were compared with that of sisal prepared by

compression moulding. Banana as well as sisal fabric composites were

also fabricated by resin transfer moulding and the mechanical properties

obtained in compression moulding were compared with that of resin

transfer moulding technique.

9.1.2. Results and Discussion

9.1.2.1. Parallel arrangement of fabrics ( ) (Compression moulding)

9.1.2.1.1. Tensile properties

Banana and sisal fibres, woven in the same pattern were used for the

composite preparation. Figure 9.1.1 shows the weave architecture used in

this experiment. In this weave pattern, only very little amount of fibre is put

in the weft direction. Hence it can be called a weftless weave. In order to

keep the warp yarns in position, fibre chord is put along the weft direction.

The distance between two fibre chord is 8 mm. Table 9.1.1 depicts the

characteristics of the woven fabric. The arrangement of three layers in

parallel way and the way of cutting the samples in the longitudinal and

transverse manner can be seen in figure 9.1.2.


Fibre chord in the weft direction

Warp yarn

Figure 9.1.1. The weave architecture

Table 9.1. 1. Characteristics of textiles used in the experiment

Material StyleDistance between fibre

chord in the weft direction(mm)

Thickness of the fabric (mm)

Banana Weftlessweave 8 1.3

Sisal Weftlessweave 8 1.5

318 Chapter 9.1

T

L

Figure 9.1.2. Arrangement of three layers of fabric in parallel way (L, longitudinal, in which samples are cut along the weave direction. (T, transverse, samples are cut perpendicular to the weave direction)

Figure 9.1.3 and 9.1.4 represent the tensile stress-strain curves of banana

and sisal fabric reinforced polyester composites prepared by compression

moulding and having one, two and three layer of fabrics; where the layers

are arranged in the parallel way and samples were cut in the longitudinal

direction. In both cases, a decrease in stress was observed in trilayer

composites and the bilayer composites showed maximum stress.


0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 20

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

Tens

ile S

tress

(MP

a)

S t r a in ( % )

B 1 B 1 1 B 1 1 1

Figure 9.1.3. Stress-strain curve of banana fabric/polyester composites [B(1)-banana; monolayer, Vf = 0.25 B(11) –bilayer, Vf = 0.45; B(111) trilayer, Vf = 0.62 ] – CM method

0 2 4 6 8 1 0 1 20

2 0

4 0

6 0

8 0

1 0 0

1 2 0

Tens

ile S

tress

(MPa

)

S t r a in ( % )

S 1 S 1 1 S 1 1 1

Figure 9.1. 4. Stress-strain curve of sisal fabric/polyester composites [S (1)-sisal; monolayer, Vf = 0.32 S(11) –bilayer; Vf =0.58 S(111) trilayer, Vf = 0.80] – CM method

320 Chapter 9.1

Figure 9.1.5 delineates the effect of volume fraction and number of layers

on tensile strength of the above composites, where longitudinal and

transverse (L & T) samples of composites are given. B represents

banana/polyester composite and S represents sisal/polyester composite.

The first, second and third points in each graph represent monolayer,

bilayer and trilayer composites respectively. Maximum tensile strength is

observed in the case of bilayer composites, when the samples are cut

longitudinally. The strength decreases in the case of the trilayer

composites. It is probably due to the inefficient wetting of the fibres with the

resin at higher volume fractions as well as the way of arranging the fibre

mat layers. In the case of trilayer composites, delamination is another

reason for the decrease in the tensile strength.

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90

20

40

60

80

100

trilayerbilayer

trilayerbilayer

monolayer

monolayer

trilayer

bilayer

monolayer

trilayer

bilayer

monolayer

Tens

ile s

treng

th (M

Pa)

Volume fraction of fibre

B (L) S (L) B (T) S (T)

Figure 9.1.5. Effect of layering pattern and volume fraction on the tensile strength of banana and sisal fabric composites [L-longitudinally cut sample; T- transversely cut sample] (CM)


Two unique positions exist in a woven fabric composite. One is the interstitial

position, which is surrounded with four different yarns and the other is

undulated position, which is defined as intersection point of warp and fill

yarns. Compared with other regions, these positions become resin rich

regions in the fibre-reinforced polymer composite Increase in the number of

layers leads to more number of interstitial positions and resin rich regions.

When the mats are arranged parallel to each other, similar regions of the mat

comes in the same position (above and below) in the composites. The

schematic representation of a typical plain weave fabric can be seen in figure

9.1.6, which shows the interstitial and undulated region.

Figure 9.1.6. Schematic representations of a typical plain weave fabric

These resin rich regions are the points where crack initiation occurs. These

cracks propagate through the resin rich regions. This ultimately leads to

crack initiation followed by delamination in the composites. The crack

propagation pattern depends on the relative direction of crack path to fibre

alignment. In other words, the fibre volume fraction and alignment of the

fabric can affect the crack-propagating pattern. In the pattern followed in

the present case, the crack propagation is found to be from warp yarn to

fibre chord through the matrix region.

322 Chapter 9.1

The tensile strength of transverse samples is very low when compared to

the longitudinal ones. In the longitudinal samples, stress is applied along

the direction of fibre length. Hence it can withstand high stress. But in the

case of transverse samples, stress is applied perpendicular to the fibre

length. Only very small amount of fibre is present in the weft region. Hence

the tensile strength is very low in these samples compared to the other.

The diameter as well as the density of sisal fibre is greater than that of

banana. Hence for the same pattern of weave, for a particular dimension,

the weight of sisal fibre will be greater than that of banana. Hence the

volume fraction of sisal will also be higher. For neat polyester, the tensile

strength is 32 MPa. By the incorporation of monolayer banana fabric

(volume fraction, 0.25), the tensile strength increases to 49 MPa. For the

bilayer composite (volume fraction 0.45), the tensile strength increases to

93 MPa, ie 190 % compared to neat polyester. With the incorporation of

bilayer sisal fabric (volume fraction, 0.58), the tensile strength increased to

98 MPa, ie 206 %. The tensile properties of banana-reinforced composite

are found to be higher than that of sisal reinforced composite.

The tensile modulus and elongation at break of the above composites are

given in table 9.1.2. For the longitudinal samples, tensile modulus

increases upto bilayer composite and decreases in trilayer. The elongation

at breaks increases with fibre content. For the transverse samples,

modulus increases as fibre loading increases. Trilayer composite shows

the maximum tensile modulus. Elongation at break of sisal fabric

composite is higher than that of banana. It is due to the higher inherent

elongation at break of sisal fibre.


Table 9.1.2. Tensile modulus, Elongation at break and flexural modulus of sisal and banana fabric composites in which layers are parallel and compression moulded.

Layering pattern

Directionof testing

Volumefraction

( Vf)

Tensilemodulus

(MPa)

Elongationat break

(%)

Flexuralmodulus

(MPa)

BB1

BB11

BB111

BB1

BB11

BB111

S1

S11

S111

S1

S11

S111

L ( )

L ( )

L ( )

T ( )

T ( )

T ( )

L ( )

L ( )

L ( )

T ( )

T ( )

T ( )

0.25

0.45

0.62

0.25

0.45

0.62

0.32

0.58

0.80

0.32

0.58

0.80

1612

2517

2280

252

495

599

2203

2947

2660

232

256

457

4.2

6.1

6.1

5.2

4.3

4.3

8.1

10.2

11.1

7.2

6.5

4.2

3782

4429

3841

442

626

466

4442

5305

5218

405

785

984

9.1.2.1.2. Flexural properties

Figure 9.1.7 delineates the flexural stress-strain graph of longitudinal

samples of sisal fabric composites having different layers. Here also, the

flexural stress is higher for the bilayer composites. The reason can be

explained as earlier.

324 Chapter 9.1

0 2 4 6 8 100

20

40

60

80

100

120

Flex

ural

Stre

ss (M

Pa)

Strain (%)

S (1) S (11) S (111)

,

Figure 9.1.7. Flexural stress-strain graph of sisal fabric composites (S1- sisal, monolayer; Vf = 0.32, S11 - bilayer; Vf = 0.58, S111 - trilayer; Vf = 0.80) CM

Figure 9.1.8 shows the effect of number of layers and volume fraction of fibre

on flexural strength in the longitudinal and transverse samples. The flexural

strength increases with fibre loading upto a particular volume fraction and then

decreases in all cases. Here also bilayer composite gives the maximum

strength. Transverse samples show very low flexural strength compared to

longitudinal samples as seen in the case of tensile strength.

The flexural modulus of the above composites is given in table 9.1.2. For the

bilayer composites, the flexural modulus is found to be very high. Compared

to monolayer composites, a tremendous increase in flexural modulus is

observed in bilayer composites. But the modulus decreases for the trilayer

composites. Since the volume fraction of sisal composite is greater than

banana in each pattern, the properties are also higher in them.


0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90

20

40

60

80

100

120

trilayerbilayer

monolayer trilayer

bilayermonolayer

trilayer

bilayer

monolayer

trilayerbilayer

monolayer

Flex

ural

stre

ngth

(MP

a)


B (L) S (L) B (T) S (T)

Figure 9.1.8. Effect of layering pattern and volume fraction on the flexural strength of banana and sisal fabric composites [L-longitudinally cut sample; T- transversely cut sample] CM

9.1.2.1.3. Impact properties

Figure 9.1.9 shows the effect of fibre volume fraction and number of layers

of the fabric on the impact strength of the composites. The impact strength

increases with fibre volume fraction and number of layers. The impact

strength of neat polyester is only 9 kJ/m2. Sisal fabric/polyester composite

shows higher impact strength compared to banana fabric composite. By

the incorporation of 0.25 Vf of banana fibre (1 layer fabric) the impact

strength increases to 222% and 0.45 volume fraction of banana fibre

(2 layers of fabric), the strength increases to 444%. By the incorporation of

0.32 Vf of sisal fibre (1 layer fabric), the impact strength increases to 577%

and 0.58 Vf of fibre (2 layers of fabric) it increases to 722%. The inherent

impact property of sisal fibre is higher than that of banana fibre. The larger

lumen size and higher microfibrillar angle of sisal fibre than banana is the

reason for this behaviour.25

326 Chapter 9.1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

10

20

30

40

50

60

70

80

90

100

trilayerbilayermonolayer

trilayerbilayer

monolayer

trilayer

bilayermonolayer

trilayerbilayer

monolayer

Impa

ct s

treng

th (k

J/m

2 )


B (L) S (L) B (T) S (T)

Figure 9.1.9. Effect of layering pattern and volume fraction on the impact strength of banana and sisal fabric composites [L-longitudinally cut sample; T- transversely cut sample] CM

9.1.2.2. Parallel and perpendicular arrangement of alternate layers ( ) by compression moulding


Figure 9.1.10 portrays the effect of volume fraction of fibre and number of

layers of woven fabric of banana and sisal on the tensile strength of the

composites in which the fabrics are arranged in parallel and perpendicular

way in alternate layers. First, second and third point in the graph represent

bilayer, ( ), trilayer, ( ) and tetralayer, ( ) composites. A

dramatic decrease in tensile properties is found in this type of composites

compared to the parallel arrangement of fabrics mentioned above. Tensile

strength increases with fibre loading upto a particular volume fraction and

then decreases in both banana and sisal composites. The properties

decreased in four-layer composite. The reason is improper wetting due to

higher volume fraction and delamination of more number of layers.


0.4 0.5 0.6 0.7 0.8 0.9 1.0

10

20

30

40

50

60

70

tetralayer

trilayer

bilayer

tetralayertrilayer

bilayer

Tens

ile s

treng

th (M

Pa)

Volume fraction of fibre.

B (l&t) S (l&t)

Figure 9.1.10. Effect of layering pattern and fibre volume fraction on tensile strength of the composites. (B l & t; banana fabrics, longitudinal and transverse arrangement in alternate layers, S l & t; sisal fabrics, longitudinal and transverse arrangement in alternate layers)

Table 9.1.3. Tensile modulus, Elongation at break and flexural modulus of sisal and Banana fabric composites in which layers are parallel and perpendicular in alternate layer and compression moulded.

Layeringpattern

Volumefraction

( Vf)

Tensilemodulus( MPa )

Elongation at break(%)

Flexuralmodulus

(MPa )

BB2

BB3

BB4

S2

S3

S4

0.43

0.64

0.81

0.57

0.78

0.92

1260

1531

1483

1110

1292

897

6.3

8.2

9.1

11.2

12.2

15.1

972

1284

1071

1228

1557

1521

328 Chapter 9.1

The tensile modulus and elongation at break of these composites can

be observed in table 9.1.3. B2, B3, B4 and S2, S3 and S4 represent bi, tri

and tetralayer composites of banana and sisal respectively. Maximum

tensile strength and tensile modulus was obtained in the trilayer

composites, where two layers are arranged in parallel and one layer in

perpendicular way. Here two layers are arranged so that the fibre length

is along the application of stress and only one layer in which the fibre

length is in the opposite direction. Tensile strength decreased in

tetralayer composite, where two layers are arranged in a parallel way

and the other two in perpendicular direction. In tetralayer composite,

lack of proper wetting also takes place due to higher fibre content.

Hence the tensile properties decrease.

9.1.2.2.2. Flexural Properties

The effect of fibre loading and number of fibre mats on flexural strength

of the composites can be observed in figure 9.1.11. The same trend in

the case of tensile strength is observed here. Flexural modulus of the

above composites can be seen in table 9.1.3. Flexural modulus is

higher in trilayer composites as observed in the case of tensile

modulus.


0.4 0.5 0.6 0.7 0.8 0.9

44

48

52

56

60

64

tetralayer

trilayer

bilayer

tetralayer

trilayer

bilayerFlex

ural

stre

ngth

(MP

a)

Volume fraction of the fibre

B (l&t) S (l&t)

Figure 9.1.11. Effect of layering pattern and fibre volume fraction on flexural strength of the composites (B l&t; banana fabrics, longitudinal and transverse arrangement in alternate layers, S l&t; sisal fabrics, longitudinal and transverse arrangement in alternate layers)

9.1.2.2.3. Impact Properties

The impact strength is very high in sisal fabric composite compared to

banana fabric (see figure 9.1.12). Here also the impact strength increases

with fibre volume fraction. When the mats are arranged parallel and

perpendicular in alternate layers, identical regions are not coming above

and below. Hence it is possible to prepare composites containing upto four

fibre mats in this pattern.

330 Chapter 9.1

0.4 0.5 0.6 0.7 0.8 0.930

40

50

60

70

80

90

100

tetralayer

tetralayer

trilayer

bilayer

trilayer

bilayer

Impa

ct s

treng

th (k

J/m

2 )


B (l&t) S (l&t)

Figure 9.1.12. Effect of layering pattern and fibre volume fraction onimpact strength of the composites (B l&t; banana fabrics, longitudinal and transverse arrangement in alternate layers, S l&t; sisal fabrics, longitudinal and transverse arrangement in alternate layers)

9.1.2.3. Parallel arrangement of fabrics ( ) (Resin transfer moulding)


By the parallel arrangement of sisal fabrics, monolayer, bilayer and trilayer

composites were prepared using resin transfer moulding. Tensile strength

was determined in the longitudinal and transverse directions using

corresponding samples. Figure 9.1.13 shows the tensile stress-strain

graph of sisal fabric composite (longitudinal sample) fabricated by resin

transfer moulding. The effect of fibre volume fraction and number of layers

on tensile strength of the longitudinal and transverse samples can be seen

in figure 9.1.14.


0 1 2 3 4 5 6 70

10

20

30

40

50

60

70

80

90

100

110

Tens

ile s

tress

(MPa

)

Strain (%)

R S1 (L) R S11 (L) R S111 (L)

Figure 9.1.13. Tensile stress-strain curve of resin transfer moulded sisal fabric composites (RS1, RTM ; sisal- monolayer, RS11- RTM sisal –bilayer, RS111; RTM- sisal trilayer - L-longitudinally cut sample)

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90

20

40

60

80

100

120


trilayerbilayer

monolayer

Tens

ile S

treng

th (M

Pa)

Volume fraction of sisal fibre mat.

R S (L) R S (T)

Figure 9.1.14. Effect of layering pattern and volume fraction on the tensile strength of sisal fabric composites by RTM [L-longitudinally cut sample; T- transversely cut sample]

332 Chapter 9.1

Tensile strength in the transverse direction is very small compared to the

longitudinal direction as that of compression moulded composites. In the

longitudinal direction, tensile strength increases with fibre volume fraction

up to 0.60 Vf and then decreases. First, second and third points represent

mono, bi and trilayer composites. From monolayer to bilayer composite,

tensile strength increases and on further increasing the layer, the strength

decreases. Compared to compression moulding, tensile strength is found

to be greater in resin transfer moulding. The monolayer composite having

volume fraction 0.32, by the compression moulding method gives a tensile

strength of 58 MPa and that of bilayer composite having 0.58 Vf , 98 MPa.

But in the case of resin transfer moulding, monolayer (0.31 Vf) and bilayer

(0.60Vf) composites show 66 and 103 MPa respectively. Fibre wetting and

fibre/matrix adhesion is higher in resin transfer moulding.

Bilayer banana composite was also fabricated by resin transfer moulding.

In the compression moulding, for a Vf of 0.45, the tensile strength was

found to be only 93 MPa. But for a volume fraction of 0.46, the tensile

strength was 112 MPa in resin transfer moulding (see figure 9.15), which

is higher value compared to sisal fabric composite. The tensile properties

of banana fibre are higher than that of sisal (see table 3.1; chapter 3). The

reason for this is the low microfibrillar angle and lower diameter of banana

fibre compared to sisal fibre.


TS FS IS0

20

40

60

80

100

120

kJ/m2

MPaMPa

Mechanical properties

Figure 9.1.15 Tensile, flexural and impact strength of bilayer banana composite prepared by RTM, Vf = 0.46

The tensile modulus and elongation at break of the resin transfer moulded

composites are presented in table 9.1.4. The tensile modulus of bilayer

sisal composite is higher than that of mono and trilayer. The tensile

modulus of resin transfer moulded composites is higher than that of

compression moulded composites. The elongation at break decreases in

RTM composites compared to CM composites. These results indicate

higher fibre/matrix interaction in resin transfer moulded composites than

compression moulded composites.

334 Chapter 9.1

Table 9.1.4. Tensile modulus, Elongation at break and flexural modulus of sisal and banana fabric composites in which layers are parallel and composites are prepared by resin transfer moulding.

Sample(layering pattern)

Directionof testing

Volumefraction

(Vf )

Tensilemodulus

(MPa)

Elongationat break

(%)

Flexuralmodulus

( MPa)

R S1

R S11

R S111

R B11

R S1

R S11

R S111

R B11

L ( )

L ( )

L ( )

L ( )

T ( )

T ( )

T ( )

T ( )

0.31

0.60

0.81

0.46

0.31

0.60

0.81

0.46

2405

3809

2770

3412

208

237

242

350

6.6

3.8

6.6

3.9

2.0

5.0

4.6

1.6

3658

5405

5052

4531

552

941

564

712

9.1.2.3.2. Flexural properties

Figure 9.16 represents the flexural stress-strain curves of resin transfer

moulded sisal fabric reinforced polyester composites having one layer, two

layer and three layer where the layers are arranged in the parallel way and

samples were cut in the longitudinal direction. Bilayer composite shows

maximum stress as seen in the compression moulding technique.


0 1 2 3 4 50

20

40

60

80

100

120

140

Flex

ural

stre

ss (M

Pa)

Strain (%)

R S(1) R S(11) R S(111)

Figure 9.1.16. Flexural stress-strain curve of resin transfer moulded sisal fabric Composites (RS1, RTM ; sisal- monolayer, RS11- RTM sisal –bilayer, RS111; RTM- sisal trilayer - L-longitudinally cut sample)

Figure 9.1.17 delineates the effect of number of layers and volume fraction

of fibre on the flexural strength of the composites. Upto bilayer composite,

flexural strength increases. But it is found to be decreased in the trilayer

composite. For a particular volume fraction and layering pattern, the

property is higher in resin transfer moulding compared to compression

moulding. This indicates a high degree of wetting in the resin transfer

moulding technique compared to the other.

336 Chapter 9.1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

20

40

60

80

100

120

trilayerbilayer

monolayer

trilayer

bilayer

monolayer

Flex

ural

Stre

ngth

(MP

a)

Volume fraction of sisal mat

R S(L) R S (T)

Figure 9.1.17. Effect of layering pattern and volume fraction on the flexural strength of sisal fabric composites by RTM [L-longitudinally cut sample T- transversely cut sample]

The void content will be less in the composite prepared by resin transfer

moulding. For the bilayer sisal composite having volume fraction 0.0.58Vf,

the flexural strength in the compression moulding technique is 94 MPa. But

for the bilayer composite of same fabric having Vf 0.60, in the resin transfer

moulding, it is found to be 103 MPa. Flexural strength increases upto 0.60

Vf, and then decreases. As observed earlier, the strength in the transverse

direction is very low when compared to the longitudinal.

Flexural strength of resin transfer moulded banana fabric composite using

two layers was also studied (figure 9.1.15). Compared to compression

moulding, tremendous increase of flexural strength was seen in resin

transfer moulding. The flexural strength of compression moulded bilayer

banana fabric composite ( Vf = 0.45) is 85 MPa, while that of resin transfer

moulded composite (Vf = 0.46) is 120 MPa. Flexural modulus also

increased tremendously.


9.1.2.3.3. Impact properties

Figure 9.1.18 represents the graph showing impact strength versus volume

fraction and number of layers of sisal fibre mat in resin transfer moulded

composites. For transverse samples, impact strength is very low compared

to longitudinal ones. As the fibre volume fraction increases the impact

strength also increases. Impact strength of resin transfer composite is

lower than that of compression moulded composites. This result indicates

better fibre/matrix interaction in resin transfer moulded composites.

0.3 0.4 0.5 0.6 0.7 0.8 0.90

10

20

30

40

50

60

70

80


trilayerbilayer

monolayer

Impa

ct S

treng

th (k

J/m

2 )

Volume fraction of sisal fibre

R S (L) R S (T)

Figure 9.18. Effect of layering pattern and volume fraction on the impact strength of sisal fabric composites by RTM [L-longitudinally cut sample; T- transversely cut sample]

The impact strength of bilayer banana fibre mat reinforced composite is

also determined. Compared to the compression moulded composite the

impact strength is slightly lowered in resin transfer moulded composite

(figure 9.1.15).

338 Chapter 9.1

Table 9.1. 5. Comparison of properties of banana and sisal fabric composites fabricated by compression and resin transfer moulding.

Method offabrication

VolumeFraction

(Vf)Layeringpattern

TensileStrength

(MPa)% of

increaseImpact

Strength(kJ/m2)

% of increase

C M

0

0.25

0.45

0.32

0.58

-

B1(L)

B11(L)

S1(L)

S11(L)

32

49

93

58

98

-

53

190

81

206

9

29

49

61

74

-

222

444

577

722

RTM

0.31

0.6

0.46

R S1 (L)

R S11(L)

R B11 (L)

65

103

112

105

221

250

57

67

47

533

644

422

Table 9.1.5 gives a comparison of tensile and impact strength of

monolayer and bilayer banana and sisal fabric composites fabricated by

compression and resin transfer moulding. Tensile strength of banana fabric

composite is higher than that of sisal. It is due to the high inherent tensile

property of banana fibre. The impact strength of sisal fabric composite is

higher than that of banana due to the high microfibrillar angle as well as

the higher lumen size of sisal fibre. The resin transfer moulded composites

show high tensile properties, compared to compression-moulded

composites. By the incorporation of 0.58-volume fraction of sisal fibre mat

(bilayer), the impact strength increases to 722% compared to neat

polyester resin.


9.1.3. Conclusions

Mechanical properties of banana and sisal woven fabric/polyester

composites prepared by compression (CM) and resin transfer moulding

(RTM) were studied. The effect of volume fraction and layering patterns on

tensile, flexural and impact properties were determined. Composites

prepared by RTM show high tensile and flexural properties compared to

compression moulding technique. The impact property is decreased in

RTM. When the fabrics are arranged in parallel way, the bilayer

composites showed the maximum tensile and flexural properties. On

further increasing the number of layer, the properties decreased. When

samples are cut longitudinally from composites, the mechanical properties

are very high. While in the transverse samples, the properties are very low.

The tensile properties of banana fabric/polyester composite are

comparatively higher than that of sisal fabric composite. But the impact

properties of sisal fabric composite are higher than that of banana for a

particular volume fraction and layering pattern. When the fabrics are

arranged in a parallel and perpendicular way in alternate layers, trilayer

composites show maximum properties. Tetralayer composites could also

be prepared in this pattern, but the tensile and flexural properties were

found to be decreased.

340 Chapter 9.1

References

1. Miryeong S., David H.S, Herbert M.W , Danny A. E., Franklin B.E.

Appl. Spectr., 60, 4 437 2006

2. Lekha K. R, Kavitha V. Geotext. Geomembr., 24, 1, 38 2006

3. Mukherjee P. S, Satyanarayana K. G. J. Mater. Sci., 19, 3925 1984

4. Scida D, Aboura Z, Benzeggagh M. L, Bocherens E. Comp. Sci. Tech.,

59, 505 1999

5. Gao F, Boniface L, Ogin S.L, Smith P.A, Greaves R.P. Comp. Sci.

Tech., 59, 123 1999

6. Bishop S. M, Curtis P.T. RAE Technical Report 83010, HMSO, London

1983

7. Shin S. G, Jang J. S. J. Mater. Sci., 35, 8, 2047 2000

8. Gommers B, Verpoest I, VanHoutte P. Acta Materialia., 46, 6, 2223

1998

9. Bhattacharya D. N, Chakravarthy I. B., Sengupta S. R. J. Sci. Ind. Res.,

20 D, 168 1961

10. Chawla K. K, Aragaor E.E.A, Monterlo R.R.C, Fernandez F.G, Moraes

M.M. Proc.3rd International Conference of Composite Materials., 1,414

1980

11. Shah A.N, Lakkad S. C . Fibre. Sci. Tech., 15, 41 1981

12. Gowda T. M, Naidu A C. B. Chhaya R. Composites., 30, 277 1999


13. Naik N. K, Kuchibhotla R. Comp. Part A., 33 697 2002

14. Sapuan S. M, Leenie A, Harimi M, Beng Y.K. Mater. Design., 27, 8, 689

2006

15. Foulk J.A, Chao W.Y, Akin D.E, Dodd R.B, Layton P.A. J. Polym.

Environ., 14, 1, 1007 2006

16. Wazzan A. A. Inter. J. Polym. Mater., 54 3 213 2005

17. Xue P, Cao J, Chen J. Comp. Struc., 70 1 585 2005

18. Tang X, Whitcomb J. D, Li Y, Sue H. J. Comp. Sci. Tech., 65 817 2005

19. Li Y, Mai L. W, Ye L. Comp. Interf., 12 1-2 141 2005

20. Pothen L. A, Thomas S, Li R.K.Y, Mai Y.W. Proc: International

Conference on Textile Composites , IIT Delhi February 2002

21. Alsina O.L.S, Carvalho L.H.D, Filho F.G.R, Almeida J.R.M.D. Polym.

Test., 24 1 81 2005

22. Jacob M, Varghese K.T, Thomas S. J. Comp. Mater., 40, 1471 2006.

23. Jacob M, Varghese K.T, Thomas S. J. Appl. Polym. Sci., 102,1,416

2006

24. Idicula M, Neelakantan N R, Oommem Z, Joseph K, Thomas S. J.

Appl. Polym. Sci ., 96, 1699 2005

25. Bledzki A. K, Gassan J. Prog . Polym. Sci., 24 , 221 1999

Chapter 9.2

Dynamic Mechanical Properties of Banana and Sisal Textile Composites Fabricated by Compression and Resin

Transfer Moulding

Abstract

This chapter deals with the dynamic mechanical properties of banana and

sisal woven fabric composites with special reference to fibre volume fraction

and layering pattern of the fabric. Storage modulus increases from monolayer

to bilayer and decreases in the trilayer composites. Tan peak was also the

minimum in the case of bilayer composites. Resin transfer moulded

composites exhibit higher storage modulus and lower damping compared to

compression-moulded composites. Banana fabric composites showed higher

storage modulus, while sisal fabric composites showed higher damping

character.

Results in this chapter have been communicated to Journal of Material Science

344 Chapter 9.2

9.2.1. Introduction

Dynamic mechanical test methods have been widely employed for

investigating the structures and viscoelastic behaviour of polymeric materials

and also for determining their relevant stiffness and damping characteristics

for various applications.1,2 The phase composition of fibre composites and its

role in determining the mechanical properties could also be investigated using

dynamic mechanical analysis. The hygroscopic behaviour of a woven fabric

carbon-epoxy composite and its effect on the viscoelastic properties and glass

transition temperature was investigated by Abot et al3 Though the viscoelastic

properties were not affected during the moisture absorption process the

plasticization effect was found to be very pronounced. The effect of alkali

treatment on the dynamic mechanical properties of kenaf and hemp fibre

reinforced polyester composites was analyzed by Aziz and Ansell.4 The

authors observed that the mechanical properties of a treated fibre composites

have higher storage modulus values and lower damping parameter which is

suggestive of the greater interfacial bond strength and adhesion between

polyester resin matrix and fibre and inferior impact properties compared to the

untreated fibre composites. They have also noticed a similar result pattern

when cashew nut shell liquid was used as matrix. Park et al.5 carried out the

impact behaviour of four layer composites through the analysis of

delamination area. It was found that the delamination area affected the impact

behaviour of the four layer composites. Kazanci et al.6 studied the viscoelastic

behaviour of filament wound polyethylene fibre reinforced polyolefin

composites. The transitions revealed during dynamic mechanical analysis

were found to be related to the branching of the copolymer.

The investigators have already reported the dynamic mechanical properties of

short banana/sisal hybrid fibre reinforced polyester composites.7 The effect of

layering pattern on storage modulus (E’), damping behaviour (tan ) and loss

Dynamic Mechanical Properties of Banana and Sisal Textile Composites… 345

modulus (E ) was studied as a function of temperature and frequency.8

Bilayer composite denoted high damping property while intimate and

banana/sisal/banana composites showed the highest stiffness. Recently,

Jacob et al.9 investigated the dynamic mechanical properties of short

oilpalm/sisal hybrid fibre reinforced rubber composites. Alkali treatment of

composites resulted in higher storage modulus values due to increased

crosslinking and formation of strong fibre /matrix interface. The composite

containing fibres treated with 4% NaOH exhibited maximum storage modulus

The study of the viscoelastic properties of woven sisal fabric reinforced rubber

composites were carried out by Thomas and coworkers.10 Storage modulus

was found to increase upon reinforcement of natural rubber with woven sisal

fabric. Chemical modification of sisal fabric resulted in a decrease of storage

modulus. In an interesting study, the dynamic mechanical analysis of woven

sisal fabric reinforced polyester composites was reported by Pothan et al.11

The impact strength of the composites increased with the number of layers

and fibre volume fraction. Storage modulus registered a dramatic increase for

composites with four layers of the fabric. However, a comparative study of

dynamic mechanical properties of woven natural fibre composites fabricated

by compression and resin transfer moulding has not been done so far.

In this study, banana and sisal in the form of textile is reinforced with polyester

resin and the dynamic mechanical properties such as storage modulus (E’),

damping behaviour (tan ) were analyzed as a function of fibre volume

fraction, number of layers and frequency. The properties of compression and

resin transfer moulded composites were compared with special reference to

banana and sisal fabrics.

346 Chapter 9.2

9.2.2. Results and Discussion 9.2.2.1. Compression moulding

9.2.2.1.1. Effect of layering pattern on storage modulus with temperature

The characteristics as well as the weave pattern of banana and sisal fabric

used for the experiment are given in chapter 9.1. The storage modulus mainly

depends upon stiffness and rigidity of a composite. Any factor that increases

the stiffness of the system will result in an increase in storage modulus.

Figure 9.2.1 represents the effect of layering pattern on storage modulus of

sisal fabric reinforced polyester composites with temperature at a frequency of

10 Hz, where, composites are fabricated by compression moulding method

and test samples are cut in the weave direction (L) of the fabric. Storage

modulus of neat polyester also can be seen. S1, S11 and S111 represent

mono, bi and trilayer composites. It can be observed that the storage modulus

decreases with temperature in all samples. In the case of neat polyester, a

large fall in modulus occurred when it is passed through the glass transition

temperature (Tg) of the matrix. It is due to the increase in segmental mobility

of the polymer chains above Tg. The drop in the modulus on passing through

Tg is comparatively less for reinforced composites than for unreinforced resin.

When sisal fabric (which is tightly knit) is incorporated in the matrix, the

stiffness of the composite increases resulting in high storage modulus.

Moreover, the addition of woven fabric allows greater stress transfer at the

interface, which consequently increases the storage modulus. It can also be

observed that storage modulus is tremendously high at the glassy region.


20 40 60 80 100 120 140 160 180 200 2202.0

2.5

3.0

3.5

4.0

4.5

5.0

Log

E'

Temperature (0C)

S1 (L) S111 (L) S11 (L) Neat polyester

Figure 9.2.1. Effect of layering pattern on storage modulus of sisal fabric reinforced polyester composites by compression moulding(S1 – sisal ; monolayer, Vf = 0.32, S11- sisal ; bilayer - Vf = 0.58, S111- sisal ; trilayer- Vf = 0.80) L-longitudinal test specimen

Storage modulus increases with fibre volume fraction to a particular level and

then decreases. The value of storage modulus is the maximum in the case of

bilayer composites.(0.58 Vf) ie. 50 % increase compared to that of monolayer

fabric. Trilayer composite shows a decrease in storage modulus value,

compared to bilayer. The decrease in storage modulus value in the trilayer

composite is probably due to the inefficient wetting of the fibres with the resin

at higher volume fraction and the delamination due to more number of layers.

This result is consistent with the enhanced tensile and flexural properties of

the bilayer composite (chapter 9.1). The tensile strength of bilayer composite

is 98 MPa, while that of monolayer composite is 58 MPa. Figure 9.2.2 shows

the effect of layering pattern of banana fabric on storage modulus with

temperature at a frequency of 10 Hz.

348 Chapter 9.2

20 40 60 80 100 120 140 160 180 200 2203.0

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

4.0

4.1

4.2

Log

E'(M

Pa)

Temperature (0C)

B111(L) B1(L) B11(L)

Figure 9.2.2. Effect of layering pattern on storage modulus of banana fabric reinforced polyester composites by compression moulding (B1- banana; monolayer, B11- banana; bilayer, B111- banana; trilayer) L-longitudinal test specimen

The same trend in sisal fabric is also observed in banana. B1, B11 and B111

represent mono, bi and trilayer banana fabric composites. The bilayer

composite having volume fraction 0.45 Vf, shows the maximum value of

storage modulus. Compared to the monolayer fabric, there is a tremendous

increase in the storage modulus of bilayer composite. Compared to the bilayer

composite a decrease in storage modulus is manifested in trilayer composite.

The same reason as in the case of sisal fabric can be explained here also.

The tensile strength, tensile modulus, flexural strength and flexural modulus of

the bilayer composites are higher compared to mono and trilayer composites

in banana as well as sisal fabric reinforced polyester composites. The authors

have already reported the effect of fibre loading and fibre ratio on the storage

modulus of short banana/sisal hybrid fibre reinforced polyester composites.8

Above Tg, the storage modulus increases with fibre loading upto a volume


fraction of 0.40 Vf. The tan delta peak height was minimum and peak width

was the maximum at 0.40 Vf. However, in the woven fabric, the increase in

the storage modulus is very high compared to that of short fibre.

Figure 9.2.3 represents the effect of storage modulus with temperature in

banana fabric composites, where the test samples are cut in the transverse

(perpendicular) to the direction of weave (T).

20 40 60 80 100 120 140 160 180 2001.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

Log

E'

Temperature (0C)

B1(T) B111(T) B11(T)

Figure 9.2.3. Effect of layering pattern on storage modulus of banana fabric reinforced polyester composites, where the test samples are cut transverse to the direction of weave (CM) B1-Vf = 0.25, B11- Vf = 0.45, B111- Vf = 0.62

In this case too storage modulus decreases with temperature in all samples,

but the decrease is not much above Tg, The storage modulus increases from

monolayer to bilayer and then decreases in the case of trilayer composites.

Bilayer composite displays the maximum storage modulus as observed in the

case of longitudinal samples. When, compared to the longitudinal samples,

the storage modulus is very low in the case of transverse samples. This result

is consistent with the tensile properties presented in chapter 9.1. When the

350 Chapter 9.2

samples are cut transversely to the weave the stress applied is

perpendicularly to the direction of fibre orientation. As a result it is incapable of

withstanding high stress. Hence properties are decreased dramatically

compared to the longitudinal samples.

9.2.2.1.2. Effect of layering pattern on tan

Damping is an important parameter related to the study of dynamic behaviour

of fibre reinforced composite structures. Tan relates to the impact resistance

of the material. As the damping peak occurs in the region of the glass

transition where the material transforms from a rigid to a more rubbery state, it

is associated with the segmental mobility within the polymer structure all of

which are initially frozen in. Therefore higher the tan peak value, greater is

the degree of molecular mobility.2 Figure 9.2.4 delineates the effect of tan

with temperature of sisal fabric reinforced polyester composites at a frequency

of 10 Hz, fabricated by compression moulding technique. The tan of neat

polyester is also given. It is observed that the gum compound exhibits

maximum damping characteristics and this damping decreases upon

reinforcement with sisal fabric. Incorporation of fabric results in the formation

of barriers that restricts the segmental mobility of the polymer chains. This

leads to lower flexibility, decreased degrees of segmental motion of the

polymer and ultimately to lower damping characteristics.


20 40 60 80 100 120 140 160 180 200 2200.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40Ta

n de

lta

Temperature (0C)

S111 (L) S11 (L) S1 (L) Neat polyester

Figure 9.2.4. Effect of layering pattern on tan of sisal fabric reinforced polyester composites by compression moulding [ S1- sisal; monolayer – Vf = 0.32, S11- sisal ; bilayer- Vf = 0.58, S111 – sisal; trilayer- Vf = 0.80]

A tremendous decrease in damping take in the case of the monolayer fabric

composite. Again it is decreased in the trilayer composite and maximum

decrease occurs in the case of bilayer composite. The tan peak height of

bilayer composite is the minimum and peak width is the maximum. The tan

peak height of trilayer composite is lower than the monolayer, while higher

than that of the bilayer composite. Bilayer composite exhibits the highest Tg,

compared to that of monolayer and trilayer. Elevation of Tg is an indication of

better fibre/matrix interaction. This result is in agreement with the results

obtained from storage modulus values. The variation of tan with temperature

in the case of banana fabric composites also can be seen in figure 9.2.5.

352 Chapter 9.2

20 40 60 80 100 120 140 160 180 200 2200.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

Tan

delta

Temperature (0C)

B111 (L) B1 (L) B11 (L)

Figure 9.2.5. Effect of layering pattern on tan of banana fabric reinforced polyester composites by compression moulding moulding [B1- banana; monolayer – Vf = 0.25, B11- banana ; bilayer- Vf= 0.45, B111 – banana; trilayer- Vf = 0.60]

In the case of banana fabric also, bilayer composite shows minimum peak

height, maximum peak width and increased Tg, compared to mono and

trilayer composites. The Tg and tan peak height values of sisal and banana

fabric composites can be observed in table 9.2.1. The decrease in fibre/matrix

interaction in the trilayer composite is due to the inefficient wetting the fabric

due to high volume fraction of the fibre and the presence of an additional

layer, which causes further delamination. The effect of tan with temperature

of transversely cut samples of banana fabric composites is shown in figure

9.2.6.


20 40 60 80 100 120 140 160 180 2000.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Tan

delta

Temperature(0C)

B1 (T) B111 (T) B11 (T)

Figure 9.2.6. Effect of tan with temperature of transversely cut samples of banana fabric composites prepared by compression moulding (T- transversely cut sample)

Damping of B1 (T) is the highest and that of B11 (T) is the lowest as observed

in the longitudinal samples. The Tg and tan peak height of these composites

can also be seen in table 9.2.1. In the transverse samples, the Tg is very low

and peak height is high, compared to the longitudinal samples. Hence

transverse samples show minimum fibre/matrix interaction. The reason

explained in the case of storage modulus can be applied here also.

354 Chapter 9.2

Table 9.2.1. Tan max (Tg) and tan peak height of banana and sisal fabric composites prepared by compression moulding

Layering Pattern

Directionof testing

Volumefraction

(Vf)

Tan max(Tg)at10 Hz (0

C)

Tan peak height at

10 Hz(cm)

gum

S1 -

S11-

S111-

B1 -

B11 -

B111 -

B1 -

B11 -

B111 -

-

L ( )

L ( )

L ( )

L ( )

L ( )

L ( )

T ( )

T ( )

T ( )

-

0.32

0.58

0.80

0.25

0.45

0.62

0.25

0.45

0.62

107.3

121.8

133.2

122

127

130

127

117

120

117

0.38

0.20

0.155

0.18

0.212

0.112

0.178

0.281

0.156

0.189

9.2.2.1.3. Effect of frequency

The mechanical behaviour of viscoelastic materials depends on time (or

frequency) as well as on temperature. The variation of dynamic properties of

the sisal fibre reinforced polypropylene with frequency has been investigated

by Joseph et al.13 The authors observed that storage modulus increased with

frequency and this increase was prominent at higher temperatures. Figure

9.2.7 shows the effect of storage modulus with temperature of bilayer

composite of banana fabric reinforced polyester composites at frequencies


0.1, 1 and 10 Hz respectively. The figure indicates the increase in storage

modulus with the increase in frequency. Modulus measurements performed

over a short time (high frequency) result in higher values whereas

measurements performed over long times (low frequency) result in lower

values. This is due to the fact that the material undergoes molecular

rearrangement in an attempt to minimise the localised stresses.14

20 40 60 80 100 120 140 160 180 200 2203.6

3.7

3.8

3.9

4.0

4.1

4.2

Log

E'

Temperature (0C)

0.1 Hz 1 Hz 10 Hz

Figure 9.2.7. Effect of frequency with temperature on storage modulus of bilayer banana fabric composites (CM)

9.2.2.1.4. Cole-cole plot

Structural changes taking place in cross-linked polymers after fibre addition

polymeric matrices can be studied using the Cole-cole method. The dynamic

mechanical properties when examined as a function of temperature and

frequency are represented on the Cole-cole complex plane,

E = f (E’) 9.2.1.

356 Chapter 9.2

Figure 9.2.8 represents the Cole-Cole plot, where the loss modulus data log

E’’ are plotted as a function of the storage modulus log E’ of the banana

fabric/polyester composites. Homogeneous polymeric systems are reported to

denote a semicircle diagram14 The Cole-Cole diagram, presented in the figure

is imperfect semicircles and the shape of the curve points towards the

relatively good fibre-matrix adhesion.

3.0 3.2 3.4 3.6 3.8 4.0 4.21.8

2.0

2.2

2.4

2.6

2.8

3.0

Log

E''

Log E'

B1 (L) B11 (L) B111 (L)

Figure 9.2.8. Cole-cole plot of compression moulded banana fabric composites

9.2.2.2. Resin transfer moulding

9.2.2.2.1. Effect of storage modulus with layering pattern

Figure 9.2.9 delineates the effect of storage modulus with temperature of

mono, bi and trilayer sisal fabric composites and bilayer banana fabric

composites prepared by resin transfer moulding. The samples for testing were

cut in the direction of weave (L) and the experiment was conducted at a

frequency of 10 Hz. The researchers are able to observe a decrease in

storage modulus with temperature in all samples. Above Tg of the matrix,


storage modulus increases with volume fraction up to 0.60 Vf (bilayer) and

then decreases (trilayer) in sisal fabric composites.

20 40 60 80 100 120 140 160 180 200 2203.6

3.7

3.8

3.9

4.0

4.1

4.2

4.3

4.4

4.5

4.6

4.7

4.8

Log

E'

Temperature (0C)

R S1(L) R S11(L) R B11(L) R S111(L)

Figure 9.2.9. Effect of layering pattern on storage modulus of sisal and banana fabric reinforced polyester composites by resin transfer moulding [ B11 – banana ; bilayer, Vf = 0.46, S1-sisal; monolayer; Vf = 0.31, S11-sisal; bilayer V f = 0.60, S111- sisal; trilayer; Vf = 0.81]

The inefficient wetting of the fabric at higher volume fraction above 0.60 Vf,

and the presence of one more layer is the reason for the low storage modulus

in the trilayer sisal fabric composite. The bilayer composite of banana fabric

(0.46Vf) shows a slight increase in storage modulus than the bilayer sisal

fabric composite (0.60Vf) in the rubbery plateau. This is due to the increased

inherent tensile strength of banana fibre when compared to that of sisal fibre.

This can be observed in table 3.1., chapter 3.

The storage modulus of resin transfer moulded composites was found to be

higher than that of compression moulded samples. The storage modulus of

bilayer sisal fabric composite, fabricated by compression moulding technique

358 Chapter 9.2

having volume fraction 0.58 Vf, is 13460 MPa, while that of resin transfer

moulded composite (0.60Vf) is 21380 MPa. The tensile, flexural and impact

behaviour of these composites are in agreement with the storage modulus

values.

9.2.2.2.2. Effect of tan on layering pattern

The damping is a sensitive indicator of all kinds of molecular motions that

takes place in a material. The high damping peaks in a composite indicate

that once the deformation is induced in a material; the material will not recover

its original shape. In a composite, the molecular motions at the interface

contribute to the damping of the material. Fibre/matrix interphase effects can

also be understood to a very good extent from the damping curves. The lower

tan delta values particularly the lower peak height associated with the glass

transition, reflects the improved load bearing properties of the system.

20 40 60 80 100 120 140 160 180 2000.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

Tan

delta

Temperature (0C)

RS1(L) RS11(L) RB11(L) RS111(L)

Figure 9.2.10. Effect of layering pattern on tan of sisal and banana fabric reinforced polyester composites by resin transfer moulding (S1- Vf = 0.31, S11- Vf = 0.60, S111- Vf = 0.81, B11- Vf = 0.46)


The effect of tan with temperature of resin transfer moulded sisal fabric

composites at 10 Hz is delineated in figure 9.2.10. The tan curve of bilayer

banana fabric composite is also manifested in this figure. The damping is higher

in the case of monolayer composite. The lower tan peak height of bilayer

composites indicate their improved load bearing properties when compared to

that of the monolayer composites. The peak height of banana fabric composite

is lower than that of sisal fabric composite. Tg is also increased in banana fabric

composites. Table 9.2.2 shows the Tg and tan peak height of the above

mentioned composites. The Tg of the bilayer composite of sisal obtained by

compression moulding is 1330C, while that of resin transfer moulding is 1420C.

In the case of bilayer banana fabric composite, the value is increased from 130

to 1430C. These results indicate the increased fibre/matrix interaction in resin

transfer moulding. The authors already reported similar behaviour in short fibre

composites. Short banana/sisal hybrid fibre reinforced polyester composites

prepared by resin transfer mouding showed enhanced tensile and flexural

properties as well as high storage modulus when compared to that of

compression moulded composites.

Table.9.2.2. Tan max (Tg) and tan peak height of banana and sisal fabric composites prepared by resin transfer moulding

RTM method- parallel

arrangement of fabrics

Directionof testing

Volumefraction

( Vf)

Tan max (Tg) at10 Hz

(0 C)

Tan peak heightat 10 Hz (cm)

Tg from E’’max at 10 Hz (0C)

R S1

R S11

R S111

R B11

L ( )

L ( )

L ( )

L ( )

0.31

0.60

0.81

0.46

140

142

130

143

0.179

0.152

0.135

0.116

120

127

107

124

360 Chapter 9.2

9.2.2.2.3. Effect of loss modulus on layering pattern

20 40 60 80 100 120 140 160 180 200

2.6

2.7

2.8

2.9

3.0

3.1

3.2

3.3

3.4

3.5Lo

g E'

'

Temperature (0C)

R S1(L) R S11 (L) R S111(L) R B11(L)

Figure 9.2.11. Effect of layering pattern on loss modulus of sisal and banana fabric reinforced polyester composites by resin transfer moulding

Figure 9.2.11 depicts the variation of loss modulus with temperature as a

function of volume fraction and layering pattern of the fabric in resin transfer

moulding. The maximum heat dissipation occurs at the temperature where E’’

is maximum indicating the Tg of the system. The Tg value is higher in the

bilayer sisal composite compared to mono and trilayer. This result is

consistent with the higher storage modulus and tan max of the bilayer

composite. The Tg values are given in table 9.2.2. The banana composite

(bilayer) also shows higher Tg.. This indicates better fibre/matrix interaction in

the bilayer composites compared to mono and trilayer composites.

9.2.3. Conclusions

Banana and sisal woven fabric composites were prepared by compression

and resin transfer moulding. The effect of layering pattern on storage modulus

and damping properties was studied as a function of temperature and

frequency. The resin transfer moulded composites showed higher storage


modulus and low damping behaviour. In the case of banana as well as sisal

fabric composites, the bilayer fabric composites showed the best properties.

The properties are found to decrease in the case of trilayer and this indicates

their poor fibre/matrix interaction. Samples tested in the direction of weave

showed enhanced properties compared to that of perpendicular direction.

References

1. Geethamma V.G, Kalaprasad G, Groeninckx G, Thomas S. Comp.

Part A., 36, 11, 1499 2005

2. Jacob M, Varghese B, Varghese K.T, Thomas S. Macr. Mol. Mater.

Eng., 291, 1119 2006

3. Abot J. L, Yasmin A, Daniel I.M. J. Reinf. Plast. Comp., 24, 2 195

2005

4. Aziz S.H, Ansell M.P. Comp. Sci. Tech., 64 , 1219 2004

5. Park R, Jang J. J. Mater. Sci ., 36, 2359 2001

6. Kazanci M, Cohn D, Marom G. J. Mater. Sci., 36, 2845 2001

7. Idicula M, Malhotra S. K, Joseph K, Thomas S. Comp. Sci. Tech., 65,

7-8,1077, 2005

8. Idicula M, Malhotra S.K, Joseph K, Thomas S. J. Appl . Polym. Sci.,

97, 5, 2168 2005

9. Jacob M, Varghese B, Varghese K.T, Thomas S. Polym. Comp., (in

press)

10. Jacob M, Jose S, Varghese K.T, Thomas S. Text. Resear. J., (in press)

11. Pothen L . A, Potschke P, Habler R, Thomas S. J. Comp. Mater., 39

1007 2005

362 Chapter 9.2

12. Gu B, Ding X. J. Comp. Mater., 39, 8, 685 2005

13. Joseph P.V, Mathew G, Joseph K, Groeninckx G, Thomas S, Comp.

Part A., 34 275 2003

14. Murayama T. Dynamic Mechanical analysis of polymeric materials.

2nd (Ed) Amsterdam: Elsevier, 1978

Documents

Woven Fabric Composites by Compression and …shodhganga.inflibnet.ac.in/bitstream/10603/7115/20/20...Chapter 9 Woven Fabric Composites by Compression and Resin Transfer Moulding Abstract