Effect of Crosslink Density on the Critical Flaw Size of a Simple Elastomer

Abstract

Abstract Tensile experiments have been carried out on a gum, amorphous EPDM elastomer. Samples with various crosslink densities and containing precuts of different lengths were tested. The energy, Wb, per unit volume, to fracture a specimen varied inversely with the length of the precut as predicted by simple tearing energy theory. Values of the inherent flaw size, Co, of the samples were determined by extrapolation of Wb to that value obtained when no intentional precut was present. Values of Co decreased with increasing crosslink density. This illustrates the decreasing ability of an elastomer network to blunt the crack tip of a stress-raising flaw as crosslinking is increased. It is suggested that this phenomenon is at least partly responsible for low values of Wb at high crosslink densities.