In practice, rubber articles often fail attributed to crack growth under static and dynamic conditions. In this work we designed various experimental methods with precut samples to characterize the effect of nanodispersed clay on the crack growth resistance. The results indicate that the incorporation of nanodispersed clay can greatly improve the crack growth resistance of natural rubber (NR)/carbon black (CB), as evidenced by the enhancement of the tensile strength under static conditions, and improvement of flex-fatigue properties under dynamic conditions, which could find wide application in the industry. Furthermore, the scanning electron microscopy (SEM) observations and molecular simulations are combined to uncover the underlying mechanism of the crack growth resistance, highlighting the enhanced polymer orientation and highly stretched ligaments, and the orientation of the clay sheets. POLYM. ENG. SCI., 2012. (C) 2011 Society of Plastics Engineers