Fracture and fatigue of silica/carbon black/natural rubber composites

J-integral theory and fatigue testing were adopted to investigate the fracture and fatigue properties of silica/carbon black (CB)/natural rubber composites with total filler content of 50 phr. Critical J-value J(IC) and tearing modulus T-R, were obtained. J(IC), as an indicator of crack initiation resistance, was dependent on the pre-cut length. T-R was related to the crack propagation of the composite. With increasing the silica/CB ratio, both J(IC) and T-R were enhanced, indicating that the resistance to crack initiation and propagation were improved. The strain energy density at a fixed strain decreased with an increase in the silica/CB ratio. Fatigue testing under constant tensile strain conditions demonstrated that the composite with higher silica/CB ratio exhibited lower cyclic crack growth rate and longer fatigue life. This was in accordance with the results of T-R, J(IC) and strain energy density of the composite, hence T-R, J(IC) and strain energy density of the composite can be used to predict its fatigue properties. (C) 2014 Elsevier Ltd. All rights reserved.