Anisotrphic Behavior of Textile Fabric

RESEARCH PROJECT ON

ANISOTROPIC BEHAVIOUR OF TEXTILE FABRICS

Prepared for: Prof. Prof. Dr.-Ing. Alexander Büsgen

Textiltechnologie, insbesondere Gewebetechnologie

Prepared by: Trisha Fatema Tuz Zhura ID 916396

Raihan Mohammad Asfi Ur ID 910398

Department: Master Textile Trade and Retail Management

Anisotropic Behaviour of textile fabric ! of !1 24

ABSTRACT

This paper contains research of ‘Anisotropic Behaviour of Textile Fabric. These tests take

consideration into the actual fabric structure along both the warp extension and weft extension,

and shear angle between warp and weft direction. The experimental analysis of the anisotropy

is realised using off-axis and linear tensile test for three types of textile fabrics. Particularly,

attention is given influence of the fabric anisotropic. Anisotropy is a characteristic of most

fabrics; the impact of the direction of loading on tensile properties can be enormous.

Anisotropy of properties comes out of anisotropy of the structure, based on longitudinal fibres.

For woven fabric there are two principal directions – warp and weft, as well as for knit fabric

Wales and Courses in which yarns and majority of fibres are oriented. Load in principal

directions results in minimum breaking elongation and maximum initial modulus. For arbitrary

force direction the values of tensile properties change and fabric deformation becomes more

complex, often incorporating fabric shears and bends deformation. Although weave anisotropy

is well known, tensile properties are usually theoretically and experimentally investigated

namely for principal directions; the main reason is probably complexity of deformation and

stress distribution when the load is put at non-principal direction. In this paper makes a

contribution to the make development of such step to describe and perhaps to overcome some

of these problems.

MOTIVATION

In today’s digital world, it is commonplace to see clothed virtual humans, or avatars, which

must interact with their surrounding environment. As part of this digital realm, the

computational modelling of clothing has seen increased attention since the late 1980’s when

Terzopoulus et al developed continuum-based models that allowed for dynamic simulations of

elastic and inelastic materials for a variety of loadings. From a modelling perspective, clothing

is treated as a layered shell consisting of multiple plies of fabric. As the human body moves, the

clothing is subjected to a variety of deformations such as stretching, shearing and bending, all

of which occur concurrently. The motivation for such clothing modelling is quite varied,

ranging from computer animation to virtual fashion design to the study of the how clothing

interacts with the wearer, the latter being of particular interest for this research. Noting the

limited number and subjectivity of available approaches for studying the mechanical


performance of protective clothing, Man and Swan [3, 7, 8] developed an analysis framework

that aimed to quantify the effects that a garment of a particular fabric, size, and fit had on the

mobility, dexterity and range-of-motion of a virtual human in order to better understand the

clothing-wearer interaction problem. Their framework separates the clothing-wearer interaction

problem into three main areas: (1) finite element modelling of fabric garments; (2) human

modelling; and (3) contact interactions between the clothing and the body and self-contact of

the clothing.

OBJECTIVE

The purpose of this research is to develop a new constitutive model that closely matches the

phenomenological response of fabrics under a variety of loadings and that will aid in the

clothing-wearer interaction study. While there are numerous types of fabrics (i.e. woven, non-

woven, knit), the research here is focused on anisotropic behaviour of textile fabrics. To this

end, the following objectives are declared: (1) use available experimental procedures to study

the behaviour of a variety of fabrics as a continuum and glean appropriate physical parameters

from the data for use in the constitutive model; (2) develop an constitutive model that features

incremental loading and unloading, thereby capturing the nonlinear, anisotropic behaviour and

employ it in a shell finite element analysis; (3) compare results from the finite element model

to experimental data; and (4) employ the constitutive model in a dynamic shell finite element

simulation. While a few nonlinear and anisotropic constitutive models exist for fabrics, the

current research: (1) addresses the symmetry assumption of orthotropic fabric models; (2)

develops a novel approach for shear parameter estimation for large deformations; and (3)

includes the hysteresis exhibited by fabrics when being unloaded.

INTRODUCTION

As practically relevant demonstrators this paper focused the complex anisotropic behaviour of

textile fabric. The textile fibres are anisotropic in nature, as the yarn in made of fibres and

fabric is made of yarn, so the anisotropic behaviour of fibres is clearly visible in the fabric. The

tensile strength of fabric plays an important role in the quality of end to product to be produce

from it. Good tensile strength relates to the good life of fabric. So the tensile strength of fabric


is checked after each chemical process especially after the weaving, knitting process before any

chemical treatment. Most of them focused on the linear uniaxial tensile Stress/Strain behaviour

along the warp, weft, and 45° oriented fabric directions. In practical use, the fabrics are often

imposed load in arbitrary direction, bi-axial load or complex load composed of elongation,

bend, shear and lateral compression. To predict tensile properties becomes more and more

important with development of technical textiles. Woven fabric is highly anisotropic, as it

exhibits different mechanical properties for different directions. An experimental approach is

applied in order to evaluate and characterise this anisotropy. Off-axis tensile testing is generally

employed for highly anisotropic composite materials. This test is a tensile test along a direction

other than warp and weft, studied the influence of varying directions of off-axis tensile tests

over the tensile and shear strength before buckling.

MECHANICAL PROPERTIES

All of these factors have a great affect on the mechanical behaviour of the fibres. Tensile tests

show that fibres exhibit a viscoelastic load response that typically includes work-hardening.

The strength of fibres can be greatly influenced by time (rate of loading and the fibres load

history), temperature and moisture. The surfaces of fibres also dictate the amount of friction

present as the fibres are spun into yarns, which influences yarn strength, elongation and

abrasion resistance among other properties. Mechanical properties of fibres are described as

follows:

Tensile strength is the tensile stress, or force per area, required to cause a material to fail.

Cross-sectional area of a fibre is difficult to determine, therefore fibre strength is measured

relative to the linear density and is referred to as tenacity. Common units for tenacity are grams

per denier, or GPD. The tenacity can be affected by the presence of moisture as some fibres

might be stronger when wet while others may be stronger when dry.

Elongation is the stretching of a fibre under a tensile force and is expressed as a percentage of

the original length. The published values of elongation are actually the breaking elongation

which is the elongation at failure.


MATERIAL AND METHOD

Modelling always means of simplification of reality and in this case idealising the form of the

load. When it wish to simulate experimental investigation of similar property, it should start

brief description of standard fabric rupture properties measuring with the use of EN ISO

13934-2 standard. Fast jaws keep the sample in original width ( width before load) what results

in tension concentration at these jaws. Break usually occurs near the sample grip sooner then

real fabric strength is reached.

The investigations were performed with three type’s lightweight fabrics samples different in

fibre content. One of them is plain weave woven fabric, another one is knit fabric and last one

warp knit or mash fabric. The principal characteristics of investigated fabrics are presented in

Table 1. The specimen test has a useful zone of 220 mm length X 110 mm width between the

grips one is based on weft (90°) direction (Figure 1) and another is warp (0°) direction (Figure

2) for each fabric.

Warp (90°)

Weft (0°)

Figure: 1

Weft (90°)

Warp (0°)

Figure: 2


The circular specimens were cut in seven angle directions (0°, 15°, 30°, 45°, 60°, 75° and 90°)

for each fabric,respectively. The forms of specimens are illustrated by the figure 3. Tests were

carried out with articulated jaws designed to allow a free rotation along the specimen’s normal

direction. Off- axis tensile test were done for all direction with the three fabrics. The strain rate

was 50mm/ min.


Table 1: Fabric Construction of particular selected apparel

EXPERIMENTAL SETUP Uniaxial and biaxial extension tests are the most common methods to determine the anisotropic

behaviour as well tensile for fabric in the warp and weft directions. While the presence of

transverse loading has been shown to have a large effect on the apparent stiffness of fabric in

the longitudinal direction due to the de-crimping and would have a significant effect on the

apparent passion´s ratio. For the research used test standard acc.to DIN EN ISO 13934-2, test

device Zwick 1455, clamps type Grab -Jaws 25x25 mm. the machine pre load 1 N and test

speed 50mm/min as well. For the test , grip to grip separation at the start position 100,00 mm

is employed where the specimen are loaded into the grips around the two stainless plate.

DIN EN ISO 13934-2 is a procedure for the determination of the maximum force of textile

fabrics known as the grab test. The method is mainly applicable to woven textile fabrics

including fabrics which exhibit stretch characteristics imparted by the presence of an

elastomeric fibre and mechanical or chemical treatment. It can be applicable to fabrics

produced by other techniques. It is not normally applicable to geo-textiles, non woven coated

fabrics, textile glass woven fabrics and fabrics made from carbon fibres or polyolefin tape

yarns. The method specifies the determination of the maximum force of test specimens is

equilibrium with the standard atmosphere for testing and of test specimens in the wet state. The

method is restricted t the use of constant rate of extension (CRE) testing machine.

Type of Fabric Yarn Fibre Fabric Areal Density (GSM )

FABRIC 1 Plain Woven 60%polyester 40% cotton

110

FABRIC 2 Weft Knit 100% cotton 120

FABRIC 3 Warp Knit (Mesh fabric )

100% polyester 100


ANISOTROPIC BEHAVIOUR

• Woven Fabric

This part of research described anisotropic behaviour of apparel and industrial light blue woven

fabric, such as tensile, bending and shear in various direction. For woven fabric there are two

principal directions- Warp and Weft, where yarns and majority of fibres are oriented. In these

research warp yarn considered as 0° and weft yarn as 90°, it was taken 2 rectangular specimen

and 7 circular specimen in different direction. Force in principal directions as rectangular and

circular result in breaking elongation. For extreme force, the values of tensile properties change

and samples become shear. All seven sample had been tested at bias angles by the DIN EN ISO

13934.

Load in variable angle of direction:

The stress strain curves of each individual sample were required over a fixed range of

elongation for the purpose of approximation. However, samples of light blue woven fabric

loaded at various bias angles for different elongation values under the preset minimum load.

Thus, all stress-strain curves were plotted from zero to a designation elongation which was

determined by the lowest elongation value of the corresponding type of fabric. From these

stress-strain behaviour of the chosen plain weave fabrics according to their simple weave

structure.

The data was recorded as Series graph.

Example for angle of load 1=0° is described Figure *. It assumed warp as 0° this specimen

loaded on preset 1N force in test device. After stress strain start, it has been seen that elongation

at break near 13.8% is influenced by 358.5N. In the similar way, all the 15° , 30°, 45°, 60° 75°

and 90° also loaded on the test device one after one and collected different elongation and

force. As example for 15° it would found 142.5N and elongation was 14.2 %. For angle of load

30° specimen shearing occurred later than previous one, force recorded as 154.8N and

elongation 25.2 %, but in 45° specimen break occurred faster than 30°. Shear happened in

146.5N load and elongation is 36.6%, which is the most highest elongation of woven fabric.

But angle of load of 60°, sample shear less than angle of 45°, it would be sheared after 32.0%

elongation in 105.1N forces. In accordance with experimental results, that the change for angle


of 75°, yarn break down earlier, it was happen after 87.24 N force and it elongated 20.4%.

Where as load in angle of 90°, it has been more force and also elongation. The value was

125.3N force and 18.6% elongation.

Graph 1

FH εH

Legend Nr N %

1=0° 358.5 13,8

2=15° 142,5 14,2

3=30° 154,8 25,2

4=45° 146,5 36,6

5=60° 105,1 32,0

6=75° 87,24 20,4

7=90° 125,4 19,6

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Graph 2

Load in diagonal direction (45°)

Load at diagonal directions is connected with shear deformation and lateral contraction

(Sun&Pan, 2005). This analysis helps with recognition of yarns spacing and angle of yarns

incline at fabric break. Elongation of woven fabric in principal directions is restricted by the

yarn system that lays in direction of imposed load, whereas load in angle of 45° with free

lateral contraction enables greater breaking strain thanks to shear deformation. For description

of fabric geometry at break it is necessary to describe jamming in the fabric; break can not

occur sooner than maximum packing density is reached. In this research its accounted that for

woven fabric in 45° angle can take the highest elongation value.

Load in rectangular direction

There is two rectangular specimen, one is considered 0° as warp direction and 90° as weft

direction. Both specimen are 200 mm X 100 mm. the test method is same as circular bias

direction. It assumed warp as 0° this specimen loaded on preset 1N force in test device. After

stress strain start, it has been seen that elongation at break near 12.4% is influenced by 322.7N.

Fn

0

100

200

300

400

0° 15° 30° 45° 60° 75° 90°

Fn


Where as load in angle of 90°, it has been seem less force and more elongation than warp yarn.

It accounted 20.2% elongation by 144N load.

Statistics Graph

Table 1 of 3Series FH εH

n = 2 N %

x 233,7 16,4

s 126,0 5,6

ν 53,91 33,71

FH εH

Legend Nr N %

1 322,7 12,4

2 144,6 20,2!

!


Series graph

Graph 3

Bar Graph

Graph 4

Fn

0

100

200

300

400

0° 90°

Fn


Anisotropy behaviour of knit woven fabric:

The Anisotropic behaviour of knitted fabric under a constant strip biaxial strain applied

instantly was estimated in the rectangular coordinate system rotated by arbitrary angle from the

structural principal axis direction. The stress relaxation mechanisms. To analyse the application

limit of the corresponding principle to an anisotropic body with the elastic behaviour, a four-

element model with two springs and two dashpots was adopted as a convenient tool. the stress

relaxation curves measured experimentally were confirmed to follow the elastic behaviour by

the four element model. The predicted curves calculated by the corresponding principle were

compared with the experimental curves, when the experiments were performed for a

rectangular coordinate system rotated by arbitrary angle from the coordinate system along the

structural principal axis direction under strip biaxial extension. The comparison provided good

agreement for the fabrics. Furthermore, as the different excitation mode, the stress relaxation

behaviour was measured for a uniaxial deformation mode with the dimension free in the

direction perpendicular to an external applied strain. The predicted curves calculated by the

corresponding principle were in fairly good agreement with the experimental curve. Thus it

turned out that the corresponding principle can be approximately applied anisotropic elastic

bodies such as fabrics.

Load in variable angle of direction:

Example for angle of load 1 assumed as 0°. For knit fabric it also assumed warp as 0° this

specimen loaded on preset 1N force in test device. After stress strain start, it has been seen that

elongation at break near 123.4% is influenced by 217.2N. In the similar way, all the 15° , 30°,

45°, 60° 75° and 90° also loaded on the test device one after one and collected different

elongation and force. As example for 15° it would found 192.7N and elongation was 111.4 %.

For angle of load 30° specimen shearing occurred slightly sooner than previous one, force

recorded as 190.2N and elongation 107 %, but in 45° specimen break occurred faster than 30°.

Shear happened in 121.1N load and elongation is 129.4%. But angle of load of 60°, sample

shear more than angle of 45°, it would be sheared after 160.6% elongation in 126.5N forces. In


accordance with experimental results, that the change for angle of 75°, yarn break down later, it

was happen after 146.3 N force and it elongated 182.8%. Where as load in angle of 90°, it has

been more force and also elongation. The value was 153.3N force and 197.6% elongation,

which is greater elongation for red knit fabric.

Series Graph

Graph 5

FH εH

Legend Nr N %

1 217,2 123,4

2 192,7 111,4

3 190,2 107,8

4 121,1 129,4

5 126,5 160,6

6 146,3 182,8

7 153,3 197,6

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Bar Graph

Graph 6

Statistic table:

Table 2 of 3Series FH εH

n = 7 N %

x 163,9 144,8

s 36,54 35,8

ν 22,30 24,68

Fn

0

75

150

225

300

0° 15° 30° 45° 60° 75° 90°

Fn


Load in rectangular direction

There is two rectangular specimen also for knit fabric, warp is considered as 0° direction and

90° as weft direction. Both specimen are 200 mm X 100 mm as like as light blue woven fabric.

The test method is same as circular bias direction. It assumed warp as 0°, this specimen loaded

on preset 1N force in test device. After stress strain start, it has been seen that elongation at

break near 110.6% is influenced by 189.3N.


It accounted 200.8% elongation by 155.3N load.

Result Table:

Graph 7

FH εH

Legend Nr N %

1 189,3 110,6

2 155,3 200,8!

!


Bar Chart of red knit rectangular fabric:

Graph 8

Statistic Table:

Fn

0

50

100

150

200

0° 90°

Fn

Table 3Series FH εH

n = 2 N %

x 172,3 155,6

s 24,04 63,8

ν 13,95 40,96


Yellow Mesh fabric:

A mesh is barrier made of connected strands of metal, fibre or other flexible/ductile materials. A mesh is similar to a web or a net in that it has many attached or woven strands. In clothing, a mesh is often defined as a loosely woven or knitted fabric that has a large number of closely spaced holes. Knitted mesh is frequently used for modern sports jersey and other clothing.

Load in variable direction for Yellow Mesh:

For yellow mesh fabric, it also assumed warp as 0° this specimen loaded on preset 1N force in

test device. After stress strain start, it has been seen that elongation at break near 49.2% is

influenced by 240.1N. In the similar way, all the 15° , 30°, 45°, 60° 75° and 90° also loaded on

the test device one after one and collected different elongation and force. As example for 15° it

would found 221.3N and elongation was 51.2%. For angle of load 30° specimen shearing

occurred sooner than previous one, force recorded as 157.9N and elongation 56.4%, but in 45°

specimen break occurred faster than 30°. Shear happened in 160.4N load and elongation is

82.2%. But angle of load of 60°, sample shear more than angle of 45°, it would be sheared after

73.6% elongation in 117.6N forces. In accordance with experimental results, that the change for

angle of 75°, yarn break down later, it was happen after 232.7 N force and it elongated 48%.

FH εH

Legend Nr N %

1= 0° 240,1 49,2

2= 15° 221,3 51,2

3 157,9 56,4

4 160,4 82,2

5 117,3 73,6

6 232,7 48,0

7 228,7 48,2

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Graph 9

Where as load in angle of 90°, it has been more force and also elongation. The value was

228.7N force and 48.2% elongation, which is greater elongation for yellow mesh fabric.

Bar chart of yellow mesh fabric in various angle:

Fn

0

75

150

225

300

0° 15° 30° 45° 60° 75° 90°

Fn


Load in rectangular direction for yellow mesh fabric:

There is two rectangular specimen also for mesh fabric, warp is considered as 0° direction and

90° as weft direction. Both specimen are 200 mm X 100 mm as like as light blue woven fabric.

and knit fabric. The test method is same as circular bias direction. It assumed warp as 0°, this

specimen loaded on preset 1N force in test device. After stress strain start, it has been seen that

elongation at break near 48.8% is influenced by 239.4N.


It accounted 86.8% elongation by 153.7N load.

Statistic Table:

FH εH

Legend Nr N %

1 239,4 48,8

2 153,7 86,8!

!

Table 4

Series FH εH

n = 2 N %

x 196,6 67,8

s 60,59 27,0

ν 30,82 39,69


Line Graph of rectangular sample of mesh fabric

Bar chart of rectangular mesh fabric

Fn

0

75

150

225

300

0° 90°

Fn


Current trends and future challenges in investigated problems:

The problem of anisotropy of woven fabric rupture properties are very complex and till now

not in the gravity centre of researches. This section could make only a short step in bringing

new knowledge on this field. Partly another to similar problem solution is used in ( Dolatabadi

et al., 2009; Dolatabadi & Kovar, 2009). Anisotropy of different fabric properties is often

investigated for textile based composites, where rupture properties are very important, for

example in ( Hofstee & van Keulen, 2000).

There are lots of possibilities how to go on in research on this topic, for example:

1. Investigation of influence of sample width on tensile properties with the goal to specify

better impact of cut yarn ends.

2. Research on biaxial and combined fabric load, the aim could be, for example, better

description of fabric behaviour at practical usage.

3. Development of suitable experimental methods and its standardisation; till now there is no

standard method for measuring rupture properties of fabrics with great lateral contraction.

4. Research of another weaves (knit, mesh), influence of structure on utilisation of strength of

used fibres.

There are other important anisotropic forms of fabric deformation, which are not described in

this paper, such as bend and shrinkage. Shear and lateral contraction is as well very important.

Conclusion

There are two limitations, firstly the plain weave fabric is easier to model, as the weakest

tangent module is around the true bias 45°. However, if the weaving structure is complex, it is

possible to have more than one locally weakest tangent module. The accuracy of this

approximation method depends on whether the data points are selected near the local weakest

longest module. Secondly, a higher degree of accuracy can only be achieved by using more

experimental data, rather than increasing the order of the trial function, meaning that the cost

will be higher.


Acknowledgement

This work was supported by the

1. Prof. Dr.-Ing. Alexander Büsgen

Textiltechnologie, insbesondere Gewebetechnologie

Webschulstr. 31

D-41065 Mönchengladbach

Telefon: +49 (0)2161 186-6024

Telefax: +49 (0)2161 186-6013

2. Michael Doerfel

Dipl.-Ing. (FH)

Hochschule Niederrhein

Fachbereich Textil- und Bekleidungstechnik

Webschulstr. 31

41065 Mönchengladbach


Appen

dix


1. Wikipedia

2. Anandjiwala, R.D. and Leaf, G.A.V. (1991), ‘Large-scale extension and recovery of plain

woven fabrics.

3. Grosberg, P.and Kedia, S (1966), ‘The mechanical properties of woven fabrics, Part 1: The

initial load extension modulus of woven fabrics’.

4. Hu, J.L., Lo,W.M. 2002. Shear Properties of Woven Fabrics in Various Directions, Textile

Research Journal, V72, pp.383-390.

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Anisotrphic Behavior of Textile Fabric