Bending Strength Index Definition

Bending Length: The part of the specimen extending from the platform, bending and drooping due to self-weight. When it in contact with the sloping line, read out the extension length, half of the extension length is the bending length of the specimen, also known as drape stiffness.

Bending Stiffness: The bending moment of a unit width specimen bending to unit curvature in a tension-free state, obtained from the bending length and the mass per unit area of the specimen, also known as bending rigidity.

Bending Stiffness Tester

Fabric stiffness tester determines the stiffness of fabric by BS 3356, BS 9073-7, and ASTM D 1388 standards. The device is used to determine the bending length and bending stiffness. The flexural modulus of the fabric can also be calculated if the mass per unit area of the fabric is known.

The Principle of Bending Stiffness Test

The specimen is placed flat on the measuring plane of the instrument, and then moving forward it slowly, so that one end of the specimen is gradually detached from the plane support and suspended. Under the influence of the gravity of the sample itself, when one end of the specimen is bent down to the inclined plane, measure the extension length and calculate the bending length and bending stiffness of the fabric by the formula.

Test Procedure

1 Take the samples from a representative section of the fabric and should not contain any folds or creases. Cut four samples of meridional and zonal by parallel or trapezoidal method, and the samples size was 200mm*25mm.

2 Adjust the instrument level. Place the sample face up on the platform, one end aligned with the front of the platform. Put up the pressure plate and make the indicator line coincide with the “zero” line of the ruler.

3 Pushing forward the pressure plate at a certain speed and driving the specimen to move forward until the specimen reaches out into contact with the inclined plane. Record the scale reading.

4 Lift the pressure plate and test the specimen back up again.

5 Calculate the arithmetic mean value by the values measured on the positive and negative sides as a reading of the extension length of the sample.

6 According to the formula, calculate the average value of warp, weft bending length and bending stiffness of the fabric.