Dynamic optomechanical behaviour investigations on undrawn polypropylene fibres

A stress-strain device is constructed and connected to a wedge interferometer. It is used to investigate interferometrically the dynamic optomechanical properties of a polymer fibre. Multiple-beam Fizeau fringes in transmission using this equipment are used for carrying out the investigation on undrawn polypropylene fibres. The mean refractive indices and birefringence are calculated at different stresses and draw ratios. An empirical formula is deduced for the relation between the stress and the mean birefringence for undrawn polypropylene fibres and the constants of this formula are determined The stress-strain diagram of this fibre is studied also. Poisson's ratio, Young's modulus, elastic shear modulus, yield stress and yield strain are calculated. Also an expression is proposed which is valid for either Young's modulus or elastic shear modulus related to the birefringence and the constants in this expression are determined for each case. The effect of stress on the refractive index profile is investigated Microinterferograms are given for illustration.