Fabric Strength Tester | Determination of Heavy Fabric Strength byHorizontal Strength Tester

Name of the Experiment: Determination of heavy fabric strength by horizontal strength tester.

Introduction:
The strength of a fabric gives us an idea how much load we can apply on it and it is very important for fabric. The strength of the fabric is very necessary for it because if the fabric strength is not good then it will break with excessive tensile force and thus the dresses produced may tear with the outside force. The strength of a fabric varies with EPI, PPI, and Count Variation. The strength of the fabric also varies if the length and width of the fabric to be tested is changed. The strength of the fabric also depends on the construction of the fabric. A plain fabric is stronger than a twill fabric if made from yarn of same count. 

Fabric Strength Tester

The m/c used here is a horizontal strength tester. Therefore, the experiment has two objects:

1. To find out the strength of the fabric.
2. To be precise in testing.

Theory:
Strength is a measure of the steady force necessary to break a material and is measured in pound. The m/c works in constant rate of extension principle. When the tension is high on the fabric then the fabric breaks.

Apparatus:

1. Heavy fabric.
2. Fabric strength tester.
3. Scissors.

M/c specification:
The Fabric Strength Tester
Goodbrand & Co. Ltd.
Capacity: 2000lb

Testing atmosphere:
Temperature – 29oC and relative humidity – 76%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.

Sample:
Size – 6inch × 2inch.
No. of sample – 20 (For warp way-10, for weft way-10).

Working procedure:

1. At first 10inch × 2inch fabric was cut out from a big piece of fabric. The excess amount of fabric was cut because the two jaws will require at least 2inch each to grip the fabric. Thus 10 samples were cut down for testing warp way strength and 10 samples for weft way strength.
2. Now, the first sample is fixed with the upper jaw J1 and the lower jaw J2.
3. The m/c is started and observed the dial until the sample is torn out.
4. When the sample is torn out the m/c is stopped and the reading is taken.
5. By this way the others’ reading are taken.
6. At last average and CV% are calculated.

Data: 
Warp way:

Reading	Fabric strength (Lbs)	Avg strength (Lbs)	SD%	CV%
1	290	300.5	3.06	4.32
2	320
3	290
4	290
5	295

Weft way:

Reading	Fabric strength (lbs)	Avg strength (lbs)	SD%	CV%
1	190	189	3.08	4.92
2	180
3	200
4	190
5	200

Calculation:
The average warp way strength = 300.5 lbs
The average weft way strength= 189 lbs

Remark:
The strength of a fabric varies with (1) EPI variation, (2) PPI variation & (3) Count variation. The strength of the fabric also varies if the length and width of the fabric to be tested is changed. If we take a sample which size is 3inch×6inch and another sample size 2inch×6inch then the strength of the first sample will be greater than the second one. Thus if we increase the length of the second sample then the strength of the second sample will be decreased. The strength of the fabric also depends on the construction of the fabric. A plain fabric is stronger than a twill fabric if made from yarn of same count. The CV% for warp =4.62% &for weft =4.92%. it means there is a lot of variation in strength of the fabric.

Crimp Percentage | Determination of Crimp Percentage

Experiment name: Determination of crimp percentage in warp and weft of a given fabric.

Introduction:
When warp and weft yarns interlace in fabric they follow a wavy or corrugated path. Crimp percentage is a measure of this waviness in yarns. Warp and weft crimp percentages are two of the eleven structural elements in fabric construction discussed by Peirce. The relationships between the geometry of a cloth structure and its physical behavior in use are complex. Although much pioneer work has been done there are many unresolved problems still to be investigated.

Objective:
To measure the crimp percentage in warp and weft of a given fabric.

Theory:
Percentage crimp is defined as the mean difference between the straightened thread length and the distance between the ends of the thread while in the cloth, expressed as a percentage. From the definition of crimp two values must be known, the cloth length from which the yarns is removed and the straightened length of the thread. In order to straighten the thread, tension must be applied, just sufficient to remove all the kinks without stretching the yarn. In practice it is seldom possible to remove all the crimp before the yarn itself begins to stretch. The standardized tensions recommended in the B.S. Handbook are given below:
 

From those two values we can calculate the crimp percentage with the following formula: 

  C=(l-p)/p*100%

where, c = crimp, l = uncrimped length and p = crimped length.

Five groups of threads selected for test are two warp way and three weft way groups. The mean crimp percentage is calculated warp way and weft way. Rectangular strips are carefully marked on the cloth and each strip cut into the form of a flap. From each strip ten threads will be removed. Removal of threads is as follows: the central part of the first thread is separated from the flap fringe by means of a dissecting needle, but the two extreme ends are left secured. One end is then removed and place in the grip of the tester, and the other end is removed and placed in the second grip. In this way the thread is transferred from the cloth to the crimp tester without loss of twist and with a minimum handling. Several crimp testers are available, Shirley crimp tester is one of them.

Atmosphere:
Temperature – 25oC and relative humidity – 67%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.

Apparatus:
1. Crimp tester
2. Fabric sample
3. Scissor
4. Scale

Sample:
Cotton woven fabric. Length = 10².

Procedure:
1. At first we have to select the warp or weft way of the fabric. Then we should select the test length of the yarn. Here it is 10².
2. According to test length we will cut the flap of fabric.
3. Now a single yarn is to remove from the flap of fabric carefully as discussed in theory.
4. One end of the yarn is gripped in the fixed gripper of the m/c and the other end is gripped in the other setting the test length.
5. Now the tension for the sample is found out from its count and it is set in the m/c.
6. After that we will apply tension along the yarn length with hand by taking away the other end of yarn far from the first end.
7. As soon as the white marl on the tension bar is on the same line of its both sides white mark, we will stop far away the other end.
8. The length of the yarn after applying tension is taken from the scale.
9. Now from this two lengths crimp percentage is calculated from the given formula.
10. In this way at least 10 crimp percentage for warp and 10 for weft is taken and average crimp percentage is calculated from them. 

Data:

S/n	Warp Yarn				Weft yarn
	Crimped length p	Uncrimped length l	Crimp percentage c	Mean	Crimped length p	Uncrimped length l	Crimp percentage c	Mean
1	10²	10.7²	7%	6.7%	10²	11.1²	11%	10.5%
2		10.9²	9%			11²	10%
3		10.8²	8%			11.2²	12%
4		10.4²	4%			11.1²	11%
5		10.6²	6%			10.9²	9%

Calculation:

Result:
Average warp crimp percentage 6.7%
and average weft crimp percentage 10.5%.

Remark:
We found that crimp percentage for warp is less than weft. It is because the warp yarns are kept in tension during weaving. Besides they are stronger and better yarn than weft. So they do not extend more. On the other hand weft yarns are kept in low tension and low in quality. So they can extend more. As a result their crimp percentage is more. We should notice that variation in crimp can give rise to faults in fabrics, e.g. reduction in strength, bright picks and diamond barring in rayons, strips in yarn dyed cloths and so on. So we should control it which is also necessary for design fabric to give required extensibility. Since crimp is related to length, it affects the amount of cloth as well as cost of production.