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 JIC and tearing modulus TR, were obtained. JIC, as an indicator of crack initiation resistance, was dependent on the pre-cut length. TR was related to the crack propagation of the composite. With increasing the silica/CB ratio, both JIC and TR 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 TR, JIC and strain energy density of the composite, hence TR, JIC and strain energy density of the composite can be used to predict its fatigue properties.