Analysis of Fatigue Crack Propagation in NR/BR Rubber Blend

Abstract

Abstract Fatigue behavior in a blend of natural rubber (NR) and polybutadiene rubber (BR) has been investigated. The energy release rates measured from load-displacement curves recorded during the fatigue test could be used to characterize the fatigue crack propagation (FCP) history of NR/BR blend. Crack propagation kinetics showed an initial low slope “ozone crack regime” with an S-shaped “mechanico-oxidative cut growth regime”. The blend has a mechanical fatigue limit of 2.4 kJ/m2. The crack initiation constituted 25% of the total fatigue life and the low slope stage comprised 40% of the crack propagation life. Examination of the fracture profile and the fracture surface revealed that microcracks and crack tip roughening were two damage mechanisms controlling the resistance to crack propagation in the “mechanico-oxidative cut growth regime”, while the reverse herringbone pattern near the notch corresponded to the “ozone crack regime”.