Tensile Strength Testing procedure for fabric or garments (Grab method)

Purpose

To determine the maximum force required to rupture (break) a woven fabric.

Principle

The centre part of the test specimen is held by grips of a specific dimension and extended at a constant rate until it ruptures (breaks). The force at which this occurs is then recorded.

Equipment

Constant rate of Extension Tensile testing instrument with the following:
• Load cell with a maximum of 1,000N capacity
• 50mm/minute constant rate of extension
• Distance between upper and lower sets of grips is 100 mm
• Pneumatic Rubber faced grips (Rear 75 x 25mm and 25 x 25mm front)
• For PC operated machines, appropriate software (to BS EN ISO 13934 Part 2;1999 )
• Printer capability

Calibrated metal ruler
Template

Specimen Preparation

-Prepare specimens, randomly selected from the fabric so that they do not contain the same warp and weft threads.

-Cut 3 rectangular specimens parallel to the warp direction and 3 rectangular specimens parallel to the weft direction.

-Each Specimen should measure 150mm in length and 100mm in width

-Place a direction line parallel to the warp on each specimen prior to removing from the fabric

Note:
The un seamed sample from Test Method 4.13 can be used for this test (this sample measures 100mm x 180).

On each specimen, carefully draw a guide line at a distance of 38mm from one of the long edges running the full length of the specimen.

Conditioning

Condition the specimens for a minimum of 4 hours in a conditioned atmosphere of 20 ± 2°C and 65 ± 2% RH before testing.

Carry out the test in this atmosphere.
Test Procedure

Using an Automatic Constant Rate of Extension Tensile Tester

a) The programme is automatic. The test speed is 50mm per minute.

b) Use the 75mm x 25mm rubber faced grip on the rear and 25mm x 25mmm grip on the front.

c) With the correct grips in place set the distance between upper and lower sets of grips to 100mm, this should be checked using a calibrated metal ruler

d) Select the correct programme and input the appropriate machine settings and fabric details etc.

e) Fix the test specimen centrally in the upper grips, so that the 38mm line drawn on the specimen coincides with one edge of the grips.

f) Close the upper grips.

g) Avoiding any pretension, adjust the specimen along the guide line into the lower grips.

h) Close the lower grips

i) Set the cross head in motion.

j) The maximum force at which the fabric ruptures (breaks) will be recorded

k) Repeat the above procedure for the remaining specimens.

Note:

- Any break which occurs within 5mm of the clamping line of the grips should be reported as a grip break

- If the grip break falls below the lowest normal break results then it should be disregarded and further samples tested

- If it falls above the lowest normal break result, then it can be included

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