A Fracture Mechanics Approach for Evaluating the Effects of Heat Aging on Fatigue Crack Growth of Vulcanized Natural Rubber

Abstract

Influence of heat aging on fatigue crack growth properties of vulcanized natural rubber used in engine mount applications were studied based on fracture mechanics approach. Heat aging of the pure shear specimens was carried out at 70°C and 100°C for a period ranging from 24h to 168h. The tearing energy at various tensile strains was calculated from the stress-strain curves obtained from the static tests of the specimens. Fatigue crack growth rate was calculated from the cyclic tests of the specimens at constant displacement conditions and results were presented as a function of tearing energy. The crack growth rate at a given tearing energy was higher for specimens aged at 100°C and increased with the increase in aging period. The crack growth rate was not much affected for the specimens aged at 70°C. Also, the effect of heat aging on molecular mobility was studied by measuring spin-spin relaxation time T2 using pulsed Nuclear Magnetic Resonance (NMR).