Bangalore
Stiffness Testing by Shirley Tester
Discover the precision of stiffness testing using the Shirley Tester. Learn how it measures fabric rigidity and drapability for quality control.
SohaniSharma
Stiffness (c) = lf (θ)
Where, f (θ) = (cos ½θ / 8 tanθ)⅓
If θ = 41.5°, then f (θ) = ½
Wet-bulb = 79
= {240 ✕ (15.5)3 ✕ 9.809 × 10-6}= 8.77 µNm
Flexural rigidity, G2 (weft wise) = (MC3 ✕ 9.809 ✕ 10-6 µNm
Introduction
Stiffness is the property by which a fabric resists deformation. Stiffness is a special property of the fabric. It is the tendency of the fabric to keep standing without any support. The handle and drape of the fabric is a key factor in the study.
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Objectives of Fabric Stiffness Testing
- To know about stiffness
- To know about the stiffness tester
- To know about the importance of stiffness test of fabric in textile.
Apparatus for Stiffness Testing
- Stiffness tester
- Scissors
- Scale etc.
Working Principle of Stiffness Testing
A rectangular strip of fabric (20 cm ✕ 2.5 cm) is mounted on a horizontal platform in such a way that it changes, like a cantilever, and bends downwards. From the length l and angle θ, a number of values are determined. The length of the fabric that will bend under its own weight to a determined, definite extent is called bending length. A measure of stiffness that determines the draping quality of a fabric. The calculation is as follows,
Where, f (θ) = (cos ½θ / 8 tanθ)⅓
If θ = 41.5°, then f (θ) = ½
So, Stiffness (c) = lf (θ) = (l × ½) = ½
The stiffness of the specimen in the warp and weft way is usually tested. The relative humidity can affect the results, so the test should be made in a standard testing atmosphere.
Atmospheric Conditions
Dry bulb = 82Wet-bulb = 79
So, from the chart Relative humidity = 66%
The figure of Shirley Stiffness Tester
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| Shirley Stiffness Tester |
The tester is made of plastic. There is a template on the top of the machine. A scale is attached to the template. The mirror and an index line are adjusted in the machine. Two side pieces support the platform and the plastic place is inclined at 41.5°.
Working Procedure of Stiffness Testing
1. First, cut the specimen in the warp and weft direction to size (20 cm ✕ 2.5 cm) with the aid of the template.
2. Then both the template and specimen are placed on the platform where the fabric is underneath.
3. Now both are slowly being pushed forward.
4. The strip of fabric will commence dropping over the edge of the template and the fabric is continued until the tip of the specimen is viewed in the mirror and cuts both index lines.
5. The stiffness can immediately be read off from the scale mark opposite the zero line engraved on the side of the platform.
6. Each specimen is tested 3 times.
7. Finally, mean values for the bending length of warp and weft directions are calculated.
Fabrics for Stiffness Testing
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| Stiffness Testing Fabrics |
Table 1: Determination of Fabric Stiffness (Warp-wise)
Table 2: Determination of Fabric Stiffness (Weft-wise)
Calculation of Stiffness Testing
Flexural rigidity, G1 (Warp wise) = (MC3 ✕ 9.809 × 10-6) µNm= {240 ✕ (15.5)3 ✕ 9.809 × 10-6}= 8.77 µNm
Flexural rigidity, G2 (weft wise) = (MC3 ✕ 9.809 ✕ 10-6 µNm
= {240 ✕ (13.13)3 ✕ 9.809 × 10-6}= 5.33 µNm
Result
The fabric stiffness (bending) warp-wise is 15.5 mmand the fabric stiffness (bending) weft-wise is 13.3 mm.
Conclusion
In this experiment, we learned about the procedure of determining fabric stiffness warp-wise and weft-wise and also learned about flexural rigidity. Fabric stiffness is one of the special properties of the fabric.
Ahmedabad
