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CHAPTER 3

EXPERIMENTAL MATERIALS AND METHODS

3.1 INTRODUCTION

The Chapter describes the materials used and methods employed in

experimentation. The constructional details of all the experimental fabrics and

the yearns used in the study are elaborated. Fabric samples with codes, which

comprised commercial fabrics, were received and tested in their finished

states only.

3.2 MATERIALS

3.2.1 Yarns and Fabrics Used in the Study

The experimental part of this work can be summarized by the

following sequence:

1. Weave a series of plain fabrics with different constructions.

2. ‘Set’ the relaxed fabric construction.

3. Test the fabric dimensional properties.

4. Test the yarn mechanical properties.

5. Test the fabric mechanical properties.

3.2.2 Weaving the Fabrics

All the fabrics were produced in the CCi Tech, Taiwan weaving

machine; this machine having the maximum reed space of 50 cm which is

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ideal for making samples. Planning for the experimental work included the

choice of a range of different plain weave constructions. With the available

range of yarn count, twist and material six fabric groups (X, Y and Z) and (A,

B and C) were woven. The warp (2/60 cotton) was common to all groups but

the weft was varied according to the scheme shown in Table 3.1.

Table 3.1 Details of weft yarns used

Fabric group Nominal linear

density (tex) Material

X 2/60 Cotton

Y 2/30 Cotton

Z 2/40 Cotton

A 2/80 Cotton

B 2/92 Cotton

C 2/100 Cotton

Details of fabrics which were used for the study of initial modulus

are given in Table 3.2.

Table 3.2 Details of fabrics

Sample No. Warp Count Weft Count EPI PPI

1 2/60s C 2/60s C 80 56

2 2/60s C 2/60s C 80 60

3 2/60s C 2/60s C 80 64

4 2/60s C 2/30s C 80 40

5 2/60s C 2/30s C 80 42

6 2/60s C 2/30s C 80 44

7 2/60s C 2/40s C 80 46

8 2/60s C 2/40s C 80 48

85

Table 3.2 (Continued)

Sample No. Warp Count Weft Count EPI PPI

9 2/60s C 2/40s C 80 52

10 2/60s C 2/80s C 80 64

11 2/60s C 2/80s C 80 68

12 2/60s C 2/80s C 80 74

13 2/60s C 2/92s C 80 70

14 2/60s C 2/92s C 80 74

15 2/60s C 2/92s C 80 78

16 2/60s C 2/100s C 80 72

17 2/60s C 2/100s C 80 76

18 2/60s C 2/100s C 80 82

Within each group the number of ends per inch, on the loom was

kept the same while three fabrics with different numbers of picks per inch

were woven. Weaving was carried out on a loom with the following

specifications.

Three groups of fabrics were produced.

Group I Five fabrics were produced from R30 Tex/2 2/20s plain, twill,

honey comb, huckaback, mockleno.

Group II Plain, 2/2 Twill, 4/4 twill, 2/2 pointed twill 8 thread twilled

hopsack, 8 thread weft sateen Honey comb, Brighten honey

comb, Huckaback, Crape 8 thread cord, Crape pin head crepe

were produced from 2/40s yarns.

Group III This group comprised of 11 samples namely, plain, 2/2 twill, 4/1

satin, crape, huckaback special honey comb, sponge, granite,

dice, 9/1 satin and 3/1 twill weave. They were produced from 40s

(14.76 tex) single yarns.

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In all the three groups, the ends and picks were kept the same and

the structures were different. These weave designs are shown in Table 3.2.

Finishing conditions were the same for all the samples. The plain weave, 2/2

twill weave and 5 harness satin weave are three fundamental textile weaves

with the following characteristics. The plain weave has many interlacements

of warp and weft yarns the 2/2 twill weave shows ridges on the fabric surface

and the 5 harness satin weave has floats. The other woven fabrics are

derivatives of these three weaves. Crape weave is a derivative of the plain

weave the sponge weave is a mixture of plain weave, the granite weave and

dice weave are derivatives of the twill weave and the 10 harness satin weave

is a derivative of the satin weave.

For determining the bending rigidity of fabrics, commercially

available fabrics were used.

The bending rigidity of fabrics was determined by a method

developed by Sun (2008). This method employs a cross-shaped specimen

with fixed strip length. The principle is similar to the cantilever type. The

distance of the fabric end from the vertical, x, and the deflection of the fabric

end from the horizontal, y, are measured (Figure 3.2).

The cross-shaped specimen has four strips with two long

dimensions parallel to warp and two long dimensions parallel to weft. Each

strip is 2.5 cm wide and 5 cm long. The size of the specimen is designed for

easy handling. A rectangular block of top area of 2.5 x 2.5 cm2 is extended

from the base and the levelness of the tester is adjustable.

A weight is placed on the centre of the specimen in order tohold the

specimen. The method of measuring ‘x’ and ‘y’ components was

accomplished by a camera and the image was fed to a computer and zoomed.

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The measurements of ‘x’ and ‘y’ components were made very conveniently.

This way provided an accurate measurement of drape and stiffness of fabrics.

Figure 3.1 Idealized bending hysteresis curve

Figure 3.2 Drape angle

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The drape angle is calculated by tan(y/x) (Figure 3.2). The

bending length C, can also be calculated by the following equation

1/3

1/3 cosG 2CW 8 tan

(3.1)

The overhang length, is equal to the strip length, 5 cm. The

measurements also were made at different orientation angle. Five tests were

done in warp and weft directions and the mean values were considered.

The cantilever bending tester was used for measuring the bending

length of fabric samples. Seams were put in horizontal and vertical directions.

3.3 TESTING THE FABRIC DIMENSIONAL PROPERTIES

3.3.1 Thread Spacings

Thread spacing is one of the fabric properties which can be

relatively easily measured in several ways. The basic principle of most of

these methods is either by counting the number of threads over a known

distance normal to the thread direction or, more accurately by precisely

measuring the distance occupied by a certain number of threads. If the

distance is ‘S’ mm and the number of threads is ‘n’ the thread spacing, p, is

given by

S

p mmn

(3.2)

The method used in the present work was to count the number of

threads in 5 cm wide samples originally prepared for the fabric tensile tests,

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using a standard counting lens, and the average of 10 readings in each fabric

direction was taken.

3.3.2 Yarn Modular Length

Modular length as defined by Nordhammar (1962) is “the average

length of yarn between two consecutive intersecting threads”. The normal

procedure to determine fractional yarn crimp in fabrics was followed for the

determination of this parameter. Yarn modular lengths (warp and weft) were

calculated from frictional yarn crimp and thread spacings in a fabric.

For the test, the fabric was laid flat, free from tension and creases.

Accurately measured flaps of 25 cm x 2.5 cm were prepared along both the

principal directions as in the case of crimp. The yarns were then frayed out of

the fabrics by means of a dissecting needle, starting from the middle. Each

yarn, when taken out, was held firmly to prevent loss of twist and both ends

were placed in the clamps of the shirley crimp tester. An average of thirty

measurements taken in groups from different places in a fabric was used to

calculate this “fundamental cloth parameter”.

Warp modular length,

1 = p2 (1+c1) (3.3)

Weft modular length

2 = p1 (1+c2) (3.4)

where p1,2 = warp and weft thread spacings respectively and c1,2 = warp and

weft frictional crimps, respectively.

90

3.3.3 Yarn crimp

The crimp of yarns (warp and weft) removed from the test fabrics

were measured on the ‘Shirley’ crimp Tester following IS:3442-1966 (1966).

Twenty measurements were made on each side and averaged. The percent

crimp was calculated by using the formula given below:

Percent crimp, C = L

x100 (3.5)

where, L = stretched length of warp/weft yarn (in cm)

= standard test length (usually, 10 cm) of yarn

Usually,

The crimp, as usually designed, is given by the fraction p

p.

More generally, the crimp is defined as the fractional excess in length

produced when straightening a crimped thread.

Weave angles 1 and 2 were calculated by the following formulae

given by Peirce (1937)

1/2

11

2

106 1p

(3.6)

1/2

22

1

106 1p

(3.7)

3.3.4 Kawabata Evaluation System for Fabric (KESF)

The KES-F system for measurement of fabric mechanical and

surface properties compresses four seperate instruments, namely KES-E-1 for

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tensile and shear testing; KES-F-2 for pure bending; KES-F-3 for

compression and KES-F-4 for surface testing as shown in table.

Table 3.3 KESF system for fabric objective measurement

Machine

Block Use Characteristic values measured

KES-F-1 Tensile and shear LT, WT, RT, EMT,G, 2HG, 2HG5

KES-F-2 Pure bending B, 2HB

KES-F-3 Compression LC, WC, RC, T

KES-F-4 Surface testing MIU, MMD, SMD

The above instruments provide hysteresis which represents the

energy loss during the complete deformation – recovery cycle as a direct

result of the inelastic mechanical processes of interfibre friction and fibre

viscoelasticity (Tables 3.3 and 3.4).

Table 3.4 Parameters describing fabric mechanical and surface properties

Parameter

symbol Description Unit

EMT Fabric extension at 5 N/cm width %

LT Linearity of load extension curve -

WT Energy in extending to 5 N/cm width J/m2

RT Tensile resilience %

Shear

G Shear, rigidity N/m

2HG Hysteresis of shear at 8; 7 m rod N/m

2HG5 Hysteresis of shear at 87 m rod N/m

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Table 3.4 (Continued)

Parameter

symbol Description Unit

Surface

MIU Coefficient of friction -

MMD Mean deviation of MIU -

SMD Geometrical roughness m

Compression

LC Linearity of compression – thickness curve -

WC Energy in compression fabric under 5 kPa J/m2

RC Compression resilience %

To Fabric thickness at 50 Pa pressure mm

Tm Fabric thickness at 5 kPa pressure mm

Weight W Mass per unit area g/m2

Digital measures characterising the fabric response to a given load

or stress are: the average slope or linearity of the curves the maximum

deformation, the energy loss or hysteresis and the residual deformation or

coercive stress. In respect of fabric surface roughness and surface friction

measurements three parameters are obtained; the mean value of the

coefficient of friction, the mean deviation of coefficient of friction, and the

surface roughness.

There are certain limitations of this system in that it is very

expensive and the primary handle provided is open to doubt due to the

questionability of collinearity of data. Pan et al (1988) have pointed out that

there are problems of uncertainty, overlapping and instability in the primary

hand values. The method of regression analysis is based on the subjective

fabric hand preferences of Japanese judges which is influenced by the

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background and cultural nature of tactile sensory assessment. Thus the results

are unsuitable in markets other than Japan.

Details of fabrics which were used to determine Drape angle,

Bending Length and Bending rigidity are given in the Table 3.5. They contain

finishes which are unknown.

Table 3.5 Details of fabrics

Fabric

No.

Warp Count

(Ne)

Weft Count

(Ne) EPI PPI Weave GSM

Thickness

(mm)

1 72 34 85 63 Plain 77.00 0.19

2 34 70 76 70 Dobby 95.00 0.25

3 66 30 108 70 Plain 95.00 0.20

4 66 32 96 62 Plain 85.00 0.20

5 68 56 100 61 Plain 88.00 0.24

6

White - 2/56,

Red(F) - 68,

White(F) - 36

32 76 63 Plain 116.00 0.25

7 66 30 96 60 Plain 91.00 0.25

8 64 32 80 66 Dobby 116.00 0.25

9 2/40 20 52 50 Plain 133.00 0.33

10 70 26 88 68 Plain 130.00 0.28

11 68 70 78 72 Plain 57.00 0.13

12 78 32 88 64 Jacquard 85.00 0.24

13 74 66 140 90 Plain 91.00 0.17

14 70 34 85 66 Plain 89.00 0.23

15 38 36 80 50 Plain 101.00 0.30

16 2/40 2/44 50 46 Plain 129.00 0.31

17 74 70 80 74 Plain 58.00 0.14

18 40 38 70 60 Plain 94.00 0.26

19 48 46 108 85 Plain 114.00 0.21

20 68 28 88 64 Plain 87.00 0.21

21 74 72 80 64 Dobby 60.00 0.15

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Table 3.5 (Continued)

Fabric

No.

Warp Count

(Ne)

Weft Count

(Ne) EPI PPI Weave GSM

Thickness

(mm)

22 63 62 148 100 Plain 96.00 0.17

23 44 42 120 72 Plain 120.00 0.25

24 2/18 2/18 46 38 Plain 243.21 0.50

25 2/30 18 53 46 Plain 161.73 0.32

26 34 Green - 2/32,

L. Green - 33 114 58 Jacquard 169.14 0.39

27 38 16 48 44 Plain 176.54 0.36

28 2/32 18 53 48 Plain 176.54 0.31

29 2/30 2/32 58 50 Plain 196.30 0.38

30

Black -

36(F), Cream

- 2/32

Black - 32(F),

Cream - 2/34 88 66

2/2

Twill 187.65 0.38

31

Lt. Brown -

38(F),

Yellow -

2/32

White - 36,

Green - 2/24 100 58 Jacquard 213.58 0.47

32 6 7 70 40 3/1 drill 455.56 0.97

33 2/44 36 100 72 Dobby 191.36 0.32

34 32 30 110 84 Dobby 186.42 0.34

35 2/44 Cream - 24,

Green - 28 116 68 Dobby 222.22 0.46

36 34 2/32 74 70 3/1 drill 228.00 0.38

37 45 110 100 75 Plain 58.00 0.17

38 70 116 122 85 Plain 74.00 0.20

39 44 57 95 82 Plain 53.00 0.19

40 42 86 100 76 Plain 62.00 0.17

41 2/100 2/100 80 72 Plain 100.00 0.22

42 48 64 88 72 Plain 84.00 0.20

43 2/80 66 78 76 Plain 81.00 0.21

44 2/102 2/96 84 72 Plain 89.00 0.23

45 42 60 86 76 Plain 91.00 0.23

46 2/108 2/88 84 74 Plain 90.00 0.21

47 2/96 78 82 76 Plain 78.00 0.20

48 44 60 89 70 Plain 98.00 0.21

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3.4 FABRICS

Five types of fabrics were used to conduct experiments for each at

different orientations (like 0º,15º,30º,45º,60º,75º and 90º). Fabrics used are

given in Table 3.6.

Shirting material – 1. 100% Cotton

2. 100% Polyester

3. Polyester cotton

Suiting material – 1. Polyester cotton

Dress material – 1. 100% Polyester

Table 3.6 Fabric Particulars

Properties

100%

Cotton

Shirting

Material

100 %

Polyester

Shirting

Material

Polyester

cotton

Shirting

Material

Polyester

cotton

Suiting

Material

100%

Polyester

Dress

Material

EPI 216 90 128 56 140

PPI 152 78 124 56 96

Warp

Count 60s 57s 57s 2/13s 57s

Weft

Count 35s 2/32s 2/28s 2/13s 80s

GSM 120 135 110 225 85

Thickness 0.24mm 0.26mm 0.26mm 0.4mm 0.22mm

3.5 SEWING THREAD

Sewing thread is an important component in a seam. Proper

selection of sewing thread is essential for achieving greater efficiency in

sewing operation.

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Particulars of the sewing thread used in this project are shown in

Table 3.7.

Table 3.7 Sewing Thread Particulars

Particulars Type

Commercial Name Madura Coats

Thread Construction Spun Yarn

Fibre Type Polyester

Ticket Number 80

No. of plies 3

3.6 METHOD USED

3.6.1 Measurement of Bending Rigidity

The Cantilever Fabric Stiffness Tester is a simple to use, rugged

instrument based on a design described in internationally recognized test

standards such as ASTM D1388. Employing the principle of cantilever

bending, a rectangular specimen is supported on a smooth low-friction

horizontal platform with a 41.5° (0.724 rad) or 45° (0.785 rad). A weighted

slide (template) is placed over the specimen and is advanced at a constant

rate. As the leading edge of the specimen projects from the platform, it bends

under its own mass. Once the material flexes enough to touch the bend angle

indicator, the test is stopped. The length of the overhang is then measured and

flexural rigidity and bending modulus can be calculated.

ASTM D1388 Standard Test Method for Stiffness of Fabrics

BS 3356 Method for determination of bending length and flexural

rigidity of fabrics

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(a)

(b)

Figure 3.3 (a) Cantilever tester without fabric strip, (b) Cantilever

tester with fabric strip [34]

3.7 SAMPLING

Fabrics were tested on bending stiffness with the seam and without

seam according to BS 3356. The dimensions of the fabric samples were 2x20

cm which were cut using template. All fabric samples were ironed at standard

98

temperature, and then conditioned at 25 2 °C and 65 2% RH for 24 hours

before testing.

3.8 TEST PLAN

Fabric samples were cut in 7 orientations ( 0º, 15º, 30º, 45º, 60º, 75º

and 90º) with respect to warp. Spun polyester yarn was used for sewing.

Fabric samples were stitched with plain seam in two different directions

(horizontal and vertical). In horizontal direction three seam allowances (5mm,

10mm and 15mm) were used (Figure 3.4).

Vertical seams Horizontal seams

(a) (b)

Figure 3.4 (a) Vertical seam in fabric sample - face (b) Horizontal seam

in fabric sample

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Fabric samples were prepared for all above mentioned orientations

at two different directions of seam for three different seam allowances and 4

readings were taken for each sample. Each test was conducted with 4

replications.

Significant test was conducted using ANOVA and the tested values

were compared with other predicted values of existing theoretical models

proposed by eminent scientists and histograms charts were drawn. The effects

of seams on the bending property were studied on radar diagram.

The flexural rigidity of yarn has often been estimated by quasi-

static beam or loop measurements (1947). However, such methods do not

provide sufficient information about the yarn bending characteristics. A more

efficient technique, using samples of parallel yarns which provides a complete

bending hysteresis carve, was therefore used in this work. The apparatus is

based on principle suggested by Livesey and Owen (1964).

3.9 SAMPLE PREPARATION

To ensure that the tested yarns were fairly representative of those in

the fabric, the following procedure was used. On the loom, after weaving each

fabric group, several reed dents were emptied of warp threads so that straight

weft threads were inserted in these sections during the ordinary, weaving

process. In the succeeding processes of finishing, these yarns received the

same treatment as the fabric. This procedure also ensured that an equal

average tension is imposed on the parallel yarns the value of which is the

same as the weaving tension.

These sections of the parallel yarns were cut into specimens of the

standard width (2.5 cm) to be tested on the bending apparatus.

100

3.10 YARN FLEXURAL RIGIDITY

Flexural rigidity is defined as the couple required to bend a material

to unit curvature.

The bending rigidity of a yarn or fabric may be differentiated into

two components: an elastic component and a non-elastic component resulting

from internal friction (coercive or frictional couple). When an applied bending

moment is released the frictional residual curvature remaining in the material

is a consequence of this non-elastic component. This phenomenon is,

illustrated by the hysteresis curve shown in Figure 3.1. The residual curvature

is given by OA and the coercive couple by OB. To exclude asymmetrical

effects these values may be expressed by

AD OC

2 and

OB OD

2

The percentage bending recovery may similarly be expressed as:

(AE CF)

100(OE OF)

If the bending behaviour of a yarn at small curvatures is to be studied,

methods such as those devised by Carlene (1950) and Peirce (1930) may be

adequate. However, these methods make the assumption of a linear

relationship between curvature and bending moment which is only true for

purely elastic materials. Alternative methods are, therefore, required when

materials such as yarns with a significant coercive couple, are bent through

large curvatures Livesey and Owen (1964) developed a pure bending (i.e.

constant curvature) test method suitable for larger curvatures which was

refined by subsequent workers (Abbott and Grosberg 1966). The method

relies upon bending a small sample between two sets of jaws, one being

101

attached to a long light arm with its centre of gravity a relatively large

distance, from the specimen. The couple bending the sample therefore,

remains virtually constant along the samples length and almost constant

curvature along the specimen is maintained as bending takes place.

3.11 TEST METHOD

The apparatus used in the present study involves bending a sample

of yarn or fabric whilst maintaining the sample in a circular arc. A different

principle to Livesey and Owen’s (1964) is used to control the relative

movement of the jaws.

3.12 TESTING PROCEDURE

For each type of yarn 8 specimens were tested. The following yarn

bending parameters were calculated: 1. The low curvature elastic flexural

rigidity, B which is the mean slope if the loop between curvatures 0 and

(0.1 mm-1

).

The coercive couple M, which is the frictional component of the

initial bending resistance and is half the width of the hysteresis loop at zero

curvature.

3.13 FABRIC TESTING

Table 3.8 gives the testing equipment and standards used for testing

crease recovery, tenacity, bursting strength and drape.

102

Table 3.8 List of the testing equipment and standard method

Experiment Testing equipment Standard method

Bending length Shirley stiffness tester ASTMD1388

Air permeability AIRTRONIC BC5636

Fabric strength Instron ASTMD2256

Fabric drape Cusick drape meter BS5058

Crease recovery Monsanto crease

recovery tester

BS3086

Water vapour

permeability

SDS, Atlas ASTME96-94

Thermal resistance

wickability

Permetest

Sinking time DIN53924

IS: 2369-1967

Wicking properties

Two standard methods are approved for wicking tests: BS3424

method 21 (1971) and 53924 (1997). The former method specifies a very long

time period (24 hours) and is intended for coated fabrics with very slow

wicking performance. In contrast DIN5 3 924 specifies a very short time for

the test, appropriate to relatively rapidly wicking fabrics.

In the current study, the standard wicking test method of DIN53924

was used for the vertical wicking test.

Distilled water was used in the experiments. The duration of every

test was 10 minutes and the interval between wicking length readings was 15

seconds. Each experiment was carried out three times. The variation of

wicking length was within +5%.

103

Prior to testing, the samples were conditioned in a standard

atmosphere of 25 ± 2°C and 65 ± 2% relative humidity for 24 hour. Sample

strips of 3.5 cm x 33 cm each were cut in the warp and weft directions from

the conditions sample. To aid observation of the wicking distance, a pen filled

will water soluble ink was used to warp a graduated scale in 1 cm intervals on

the strips. The samples were then mounted on the pinned frame for the

vertical tests. The dipping ends of the samples were aligned leaving a length

of 1 cm to dip into the infinite reservoir containing distilled water. A ruler

with a millimetre divisions was placed parallel to the sample strip enhance the

accuracy of the measurement.

The height of the advancing liquid front as a function of time was

recorded by visual observation of the running ink through a travelling

microscope at 5 minute intervals for the first hour and then at hourly intervals

thereafter until the maximum wicking height (equilibrium point) was reached.

To avoid contamination by the ink the test liquid was changed after each test.

Constant temperature and humidity in the ambient, atmosphere were achieved

by testing in the conditioned room.

The strip method has been used by Holmerk and Peer (1988) to

characterize the wicking behaviour of proves materials and they found it

readily applicable under different conditions with a relatively high degree of

reproducibility Zhunns (2001) also found good.

Zhuang (2002) also found good correlation between results

obtained by manual and automatic testing.