Fatigue Resistance and Dynamic Crack Growth Behavior of Carbon Black/Styrene–Butadiene Rubber Composites

Fatigue is one of the main ways that rubber products are damaged, and its mechanism is so intricate that no definitive conclusion has been reached so far. This work investigates the effects of styrene chain segment content, carbon black (CB) content, and their combined effect on the dynamic fatigue behavior and crack propagation mechanism of styrene–butadiene rubber (SBR) composites. During this process, the methods of J-Integral and true stress are applied to study the dynamic fatigue crack propagation behavior. The results show that CB and styrene chain segments exert a combined effect on the fatigue performance of the composites. The increase in styrene chain segment content enhances the rigidity of the composites, and combined with the reinforcing effect of an appropriate CB loading, the CB20/SBR40 composite thus exhibits the highest fatigue life. The magnitude of the J-integral value can preliminarily indicate the resistance of CB/SBR composites to fatigue failure. During the dynamic fatigue process, the number of fatigue cycles when the true stress shifts from a stable state to a rapid increase is consistent with the number of cycles when the fatigue crack transitions from stable to rapid propagation. This indicates that the change in true stress can serve to characterize the dynamic fatigue behavior of CB/SBR composites, providing a realistic and engineering-applicable method for the study of fatigue fracture behavior in rubber composites.