An analysis of thickness effects in the Izod test

The Izod impact test is analyzed numerically using a polymer constitutive relation with material parameters qualitatively representative of a polycarbonate. The computations are full 3D transient analyses using explicit time integration and accounting for finite strains. The main purpose of the analyses is a comparison of the stress and strain fields that develop for the various specimen geometries that are used in practice, ranging from a specimen with a square cross-section to a specimen with a width about a quarter of that value. It is shown that the response varies from something close to a plane strain response to something close to a plane stress response. The results illustrate the effect of the stress–strain behavior of polymers, which involves attaining a stress peak, followed by softening and then by the gradual evolution of a very stiff response resulting from increasing network stiffness.