How do you design and conduct a fabric testing experiment that follows the relevant standards and guidelines?

1 What is Poisson's ratio?

Poisson's ratio is a dimensionless number that describes how a material changes its shape when it is stretched or compressed. It is defined as the negative ratio of the lateral strain (the change in width or thickness) to the axial strain (the change in length) along the direction of the applied force. For example, if a fabric sample is stretched by 10% in length and contracts by 5% in width, its Poisson's ratio is -0.5. A high Poisson's ratio means that the material tends to contract more when stretched, while a low Poisson's ratio means that the material tends to maintain its shape when stretched.

2 What is shear modulus?

Shear modulus is a measure of the rigidity or stiffness of a material when it is subjected to a shear force, which is a force that causes two parallel layers of the material to slide past each other. It is defined as the ratio of the shear stress (the force per unit area) to the shear strain (the angular displacement of the layers) in the plane of the force. For example, if a fabric sample is twisted by 10 degrees and the shear stress is 100 kPa, its shear modulus is 10 kPa/degree. A high shear modulus means that the material resists deformation when twisted, while a low shear modulus means that the material easily deforms when twisted.

4 How to prepare fabric samples for testing?

Before you perform the tests, you need to prepare your fabric samples according to the standards and guidelines that apply to your specific product or application. For example, if you are testing fabrics for clothing, you may need to follow the ASTM D5034 standard, which specifies the dimensions, number, and conditioning of fabric specimens for tensile testing. If you are testing fabrics for industrial use, you may need to follow the ISO 13934-1 standard, which specifies the method, apparatus, and calculation of fabric tensile strength and elongation. You also need to make sure that your fabric samples are free of defects, wrinkles, folds, or creases that may affect the test results.

5 How to perform the tests and calculate the parameters?

Once you have prepared your fabric samples, you can perform the tests using the tensile testing machine and the shear testing device. You need to attach your fabric samples to the clamps or grips of the devices, and set the parameters such as the force, speed, and direction of the tests. You also need to calibrate the devices and ensure that they are working properly. During the tests, you need to record the data such as the force, displacement, width, thickness, angle, and torque of your fabric samples. After the tests, you can calculate the Poisson's ratio and shear modulus of your fabrics using the formulas:

Poisson's ratio = - (lateral strain / axial strain)

Shear modulus = (shear stress / shear strain)

You can also use software or online tools to help you with the calculations and data analysis.