# How to Determine Fabric Strength by Vertical Strength Tester

Last Updated on 13/04/2021

Name of the Experiment:
How to determine light fabric strength by vertical Strength Tester with pendulum lever principle.

Introduction:
Determine strength is very important for any fabric. The strength of a fabric gives us an idea how much load we can apply on it. 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. The machine used here is a vertical strength tester.

Objectives:

1. To determine 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 machine works in Pendulum lever principle with constant rate of extension.

Assuming the specimen to be extensible and an absence of any dynamic effects, we get from the figure:

Fr = Mgr = MgRsinθ

As the value of M, g, R and r are constant, therefore

F α sinθ

According to the applied force the m/c dial gives us the strength in lb on the basis of this θ.

Apparatus:

1. Cotton fabric
2. Vertical strength tester
3. Scissors

Machine specification:

• Name: The Fabric Strength Tester
• Brand: Goodbrand & Co. Ltd.
• Capacity: 250lb

Testing atmosphere:

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

Sample:

• Size – 8inch x 2inch.
• No. of sample – 20 (For warp way-10, For weft way-10).

Working procedure to determine fabric strength:

1. At first 12inch × 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.
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.

Experimental Data:

Warp way:

 Reading Fabric strength (lbs) Avg strength (lbs) SD CV% 1 80 82.3 3.23 3.92 2 87 3 86 4 78 5 80

Weft way:

 Reading Fabric strength (lbs) Avg strength (lbs) SD% CV% 1 71 70.4 2.9 4.24 2 64 3 69 4 72 5 74

Calculation:

………………………………………………80 + 87 + 86 + 78 + 80 + 85 + 84 + 80 + 79 + 84
The average warp way strength = —————————————————————————–
……………………………………………………………………………….10
= 82.3

………………………………………………71 + 64 + 69 + 72 + 74 + 70 + 68 + 74 + 70 + 22
The average weft way strength = —————————————————————————–
………………………………………………………………………………10
= 70.4

Result:

1. The warp way fabric strength = 82.3 lbs
2. The weft way fabric strength = 70.4 lbs
3. The CV% for warp way fabric strength = 3.92%
4. The CV% for weft way fabric strength = 4.24%

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.

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