WOVEN FABRICS

W.I. SamarasingheTextile Technologist

Sri Lanka Institute of Textile & Apparel

Fabric Definition

A manufactured assembly of fibres

and/or yarns, which has substantial

surface area in relation to its thickness

and sufficient mechanical strength to

give the assembly inherent cohesion.

Fabrics can be produced by variety of methodsWeaving Woven fabrics

Knitting Knitted Fabrics

Bonding or Non-wovenFushing fabrics

Knitting - Knitting is a process to produce a fabric which is formed intermeshing of loops by using a continuous yarn or set of yarn.Weaving - Weaving is a produce to produce a fabric by interlacing two set of flexible material at right angle to each other.Nonwoven - Non-woven is a process to produce fabric directly from webs of fibres by bonding or fusing by interlocking.

A woven fabric is produced by interlacing

two sets of yarns, the warp and the weft,

which are at right angle to each other in

the plane of the fabric. The warp is

oriented in the direction of the length of

the fabric, and the weft in that of its

width. Individual warp and weft yarns

are called ends and picks. Interlacing of

the ends and picks with each other

produce a coherent structure. The

repeating pattern of interlacing is called

the weave.

Woven Fabric Structure

Warp - The lengthwise set of yarn in a loom which forms the lengthwise threads of the fabric produced.

Elements of woven fabric structure.

End - A single warp yarn is known as an end.Weft - The thread inserted across the width of the fabric, which form the crosswise threads of a fabric.Picks- Each crosswise yarn is a pick.

The width of a fabric - The perpendicular distance between the two edges of the fabric in the direction of the weft.

Warp Count : The unit used to define the thickness

or diameter of the yarn used. Weft Count : The unit used to define the thickness or diameter of the yarn used as weft. Warp Density : The number of warp threads per unit length. Ex: Ends per inch or Ends per cm Weft Density : The number of weft threads per unit

length Ex: Picks per inch or Picks per cm

Weave : The order in which the warp and weft threads are interlaced in the fabric. Type of Yarn : The composition of the fibres which form the yarn. Ex. 100% Cotton, 65/35 Polyester Cotton, 100% Rayon Finish : This includes the finish given to the

fabric. Ex. (i) Grey - Fabric in loom state is without undergoing any finish. (ii) Bleached – A fabric that has been bleached.

Fabric Notation The parameters by which a fabric is identified or described.

Warp count x Weft count Width, Weave, Warp density x Weft density Yarn type, Finish

Eg. 30 Ne x 20 Ne 63”, Plain weave, 72 epi x 50 ppi 100% Cotton, Grey

Woven Fabric Structure is depend on following parameters 1. The weave2. The thread densities in warp and weft3. The coarseness or fineness of the warp

and weft yarn.4. The weariness of warp and weft

Influences of parameters on Fabric Properties 1. Fabric weight2. Fabric thickness3. Fabric width and length4. Breaking load and extension5. Cover and permeability

The Weave

The basic weaves : 1. Plain weave 2. Twill weave 3. Satin & Sateen

weave

Representing Methods

of Weave

Point paper representation

Thread diagramCross section

The repeating pattern of interlacing is called weave.

Warp & Weft Crimp Interlacing causes the warp and weft yarns to assume a wavy configuration, the plane of the weave being substantially perpendicular to that of the fabric. This waviness is called crimp. Crimp is stated quantitatively either as a fraction c or as a percentage c percent. c = Ly – Lf and c percent = (Ly – Lf) x 100

Lf LfWhere Ly = the uncrimped length of the yarn. Lf = its extent in the fabricThe expression c = Ly – Lf may be written c = Ly – 1 Lf Lffrom which (1 + c) = Ly/Lf (1+c) is called the crimp ratio.

Fabric Weight

Fabric weight influences

materially certain fabric

properties such as drape handle.

It is obviously necessary to be

able to calculate the weight of

warp and weft yarn in a given

length of cloth, both for the

purpose of ordering the yarn and

of costing the cloth.

Warp & Weft Weight Calculation To do this following date should be

available.

1.Length and width of the cloth

2. The ends and picks per inch

3. The warp and weft counts

4. The warp and weft crimp

5. Let W = the weight of the warp or

weft (ib)

W = Total length of yarn (yd)

Yards/lb of yarn

Cover Factor, k

The ratio yarn diameter;

thread spacing (d/p)

expresses the relative

closeness of a set of

uniformly spaced,

parallel threads, such as

the warp or weft in a

woven fabric. Relative

closeness influences

materially certain fabric

properties such as

firmness, handle and

drape,

d

P

Cover Factor, k contd. No. of threads/inch – n

the reciprocal of the threads per inch, p = 1/n

d = 1 (in) 28N

Peirce’s formula for yarn diameters.N is cotton count (it is necessary to convert the yarn number to the corresponding cotton counts before using this equation.)

Cover Factor, k contd. The ratio d/p also express the fraction of the area of the cloth covered by the warp or weft yarns. We may therefore call it the fractional cover is,

fractional cover = d/p

substituting Peirce’s estimate of yarn diameter d = 1 28 N d = 1 p 28 N x 1/p d = n p 28 N

Cover Factor, k contd.

d/p has value 1.0 when the yarns are just touching.

K = 28

K = 14

K = 7

Peirce multiplied the equation by 28 to eliminate the numerical constant 28 and defined the result as the ‘Cover Factor k.’

Cover Factor, k contd.

Cover Factor k = n/N because we have multiplied by 28, cover factor as defined in equation has a value of 28 when yarn are just touching.

It is usual to calculate separate cover factors for the warp and weft. The sum of the warp and weft cover factors is known as the cloth cover factor Kc.

Plain Weave

In this simplest weave, the weft pass over one warp yarn and under the next alternating in this manner once across the cloth. The second time across, the weft pass over the warp yarn it went under, and under the warp it went over on the previous row. The third time across is a repetition of the first.

Plain Weave contd.

WA

RP

1 W

AR

P

2 WA

RP

3 W

AR

P

4

PICK 1

PICK 2

PICK 3

PICK 4

Plain Weave contd. Since plain weave has the maximum possible frequency of interlacing. It tends to be firm and resist slipping. The weaving process is comparatively inexpensive because the design is so simple.

Plain weave cloth can be cleaned easily, and when firm and closely woven they wear well.

Plain, weave fabrics are produced generally for the following end used.

Shirtings, Dress fabrics, Sheetings, Canvas, Handkerchief etc.

Twill Weave In this weave weft yarn are interlaced with warp yarn in such a way as to form diagonal lines across the fabric.

Following diagram illustrates a simple twill weave.

WA

RP

1 W

AR

P

2 WA

RP

3 W

AR

P

4

PICK 1

PICK 2

PICK 3

PICK 4

WA

RP

5 W

AR

P

6

PICK 5

2/2 TWILL WEAVE

Twill Weave contd. The weft yarn passes over to and under two warp yarns, alternating across the cloth. The second weft or pick passes over two and under two warp yarns. But it laps back on the ground previous row, thus forming a stair pattern.

This type of twills are called even or balanced twills.

Twill Weave contd. In an unbalanced or uneven twill either the warp or the weft floats predominate.

Twill is the most durable of all weaves. It has more number of regular floats than any other weave. Therefore it makes fabric closer in texture, heavier and stronger than plain weave. This is why twills are more suitable for men’s clothing fabrics.

Twill Weave contd. Also it is possible to produce more fancy designs in twills than in plain weaves. Twill weaves do not show dirt so quickly as plain weave, but once they are dirty they are harder to clean.

Cloth made in twill weaves may be classified as follows.•Denim

•Men’s cloth (suitings)

•Table cloth•Flannel etc.

Satin and Sateens Why do satins have shining effect? Any consumer may have asked this question. The answer is that the type of cloth construction called the satin weave gives great shining effect to a fabric and reflects the light better than dull-finished fabrics in plain or twill weaves do.

Satin and Sateens Contd. The consumer should notice that whenever they feel a silk, polyester or rayon dress stain, the hand slips more easily length wise than cross wise of the fabric. The reason is that more warps than weft yarns are exposed on this side. If the fabric is turned over, more wefts than warps are visible.

Satin and Sateens Contd. Following diagram shows two-diagrams of SATIN and SATEEN weaves.

1

2

3

4

5

SATIN WEAVE

SATEEN WEAVE

1

2

3

4

5

1 2 3 4 5 1 2 3 4 5

Satin Formerly, cotton warp satin was often used for linings, slippers and furnishing.

Nowadays a very large proportion of satin is made from viscose, cellulose acetate and nylon.

The materials that are made in the satin weave include.• Bridal satin

• Dress satin• Slipper satin• Coat linings etc.