A METHOD OF DETERMINING THE SHEAR MODULUS AND POISSONS RATIO OF POLYMER MATERIALS

An experimental method is described which allows the shear modulus and Poisson's ratio of a polymer material to be determined as functions o f temperature. Using commercial thermal mechanical analysis equipment, measurements are required of the thermal expansion coefficients of bo th unconstrained and constrained specimens, and of the Young's modulus . The constraint on a small disc-shaped polymer specimen is applied by a copper annulus. The basis of the method is that the apparent therma l expansion of the constrained specimen depends on the Poisson effect, and an analysis is given which enbles the Poisson's ratio to be deter mined. Some illustrative results are presented for a silicon rubber.