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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
Anisotropic Behaviour of textile fabric ! of !2 24
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
Anisotropic Behaviour of textile fabric ! of !3 24
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.
Anisotropic Behaviour of textile fabric ! of !4 24
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
Anisotropic Behaviour of textile fabric ! of !5 24
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.
Anisotropic Behaviour of textile fabric ! of !6 24
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 of textile fabric ! of !7 24
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
Anisotropic Behaviour of textile fabric ! of !8 24
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
!
!
!
!
!
!
!
Anisotropic Behaviour of textile fabric ! of !9 24
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
Anisotropic Behaviour of textile fabric ! of !10 24
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!
!
Anisotropic Behaviour of textile fabric ! of !11 24
Series graph
Graph 3
Bar Graph
Graph 4
Fn
0
100
200
300
400
0° 90°
Fn
Anisotropic Behaviour of textile fabric ! of !12 24
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
Anisotropic Behaviour of textile fabric ! of !13 24
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
�
�
�
�
�
�
�
Anisotropic Behaviour of textile fabric ! of !14 24
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
Anisotropic Behaviour of textile fabric ! of !15 24
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.
Where as load in angle of 90°, it has been seem less force and more elongation than warp yarn.
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!
!
Anisotropic Behaviour of textile fabric ! of !16 24
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
Anisotropic Behaviour of textile fabric ! of !17 24
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
!
!
!
!
!
!
!
Anisotropic Behaviour of textile fabric ! of !18 24
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
Anisotropic Behaviour of textile fabric ! of !19 24
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.
Where as load in angle of 90°, it has been seem less force and more elongation than warp yarn.
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
Anisotropic Behaviour of textile fabric ! of !20 24
Line Graph of rectangular sample of mesh fabric
Bar chart of rectangular mesh fabric
Fn
0
75
150
225
300
0° 90°
Fn
Anisotropic Behaviour of textile fabric ! of !21 24
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.
Anisotropic Behaviour of textile fabric ! of !22 24
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
Anisotropic Behaviour of textile fabric ! of !23 24
Appen
dix
Anisotropic Behaviour of textile fabric ! of !24 24
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.