Thursday, June 10, 2021

Fabric tensile strength test

 

Fabric tensile strength test:

 

Tensile strength of fabric:

 

When the stretching force (load) is applied to the fabric, it begins to elongate. As the stretching force (load) increases gradually, the elongation also increases. When the amount of stretching force reaches a certain point, the fabric begins to break. Now we can say that the tensile strength of the fabric is the amount of stretching force (load) at which the fabric begins to break when it comes under stretching conditions. It is measured in Newtons, pounds, or kilogram-force. It depends upon the yarn strength, material type or thread count per square inch of the fabric etc. The tensile strength of the fabric is determined separately in the warp and weft direction.

 

Synthetic fabrics have better tensile strength than natural fabrics.

 

The fabric made of fine and long-staple fibres poses higher tensile strength than coarse and short fibres.

 

If the warp and the weft count of two fabrics are same, then the fabric having more threads per square inch will give a higher tensile strength.

 

Fabric tensile strength test:

 

There are two types of methods used for testing of fabric tensile strength:

 

11 - Strip test

22 - Grab test

 

Strip test:


In this test, the full width of the specimen is gripped between gripping jaws and stretched. The whole test is completed in below steps:

 

Apparatus used:

 

11- Fabric tensile strength tester

22- Fabric swatch

33- Scissor

44- Marking pen

55- Magnifying glass

66- Marking template

77- Needle

 

Specimens preparation:

 

The fabric tensile strength is determined in warp and weft direction separately.

 

First of all, the warp and weft direction of the fabric is identified carefully with the help of magnifying glass.

 

Now, a number of specimens from warp and weft directions are prepared according to the testing standard. 5 specimens from each direction are prepared.

In many testing standard procedures, the length of the test specimen is kept 200 mm or 8 inches and the width of the specimen is kept 50 mm or 2 inches.

 

The gripping margin is also taken in the length direction according to the gripping jaws of the testing instrument.

The warp or weft threads of the specimens are aligned by removing the threads of edges of width sides with the help of a needle. You can see the below pictures:


Testing method:

First of all, the warp specimens are tested one by one. The specimen is tightened between fixed and movable gripping jaws carefully. please see the below picture:

 




The specimen length between both gripping jaws is kept 200 mm accurately.

 

Now, the reading of the load cell is observed in relaxed condition.

 

The power supply is switched on now.

 

The movable jaws begin to travel and they apply a stretching force upon the specimen.

 

When the stretching force reaches a certain limit, the specimen gets broken.

 

The breaking load is recorded automatically in the load cell.

 

The breaking force is noted now.

 

The difference between the last reading and initial reading is calculated.  

 

This difference is the tensile strength of the fabric.

Grab test: 


The specimen size is kept 6” x 4” in this method. Only one inch of the specimen width is gripped by fixed and movable gripping jaws. The stretching force gets applied upon only one-inch wide strip. 1.5” margin at both sides of the specimen width is kept unclamped at the top and bottom sides of the specimen. The distance between both gripping jaws is kept 6”. The rest of the testing method gets similar to the strip test. you can understand the clamping method by the below picture:


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