Multiaxial stress effects on fatigue behavior of filled natural rubber

This work explores multiaxial stress effects on fatigue crack nucleation and growth in filled natural rubber based on experiments using short thin-walled cylindrical specimens subjected to axial and twist displacements. Cyclic stress–strain response exhibits significant initial softening relative to the monotonic response, followed by a more gradual additional softening. Irreversible breakage of various types of bonds is believed to cause the initial softening, while the presence of fillers and their influence on network chain breakage is believed to cause the additional softening. Crack nucleation planes and crack growth paths were monitored and cracks were observed to form on specific plane(s). Correlations of crack nucleation lives and growth rates with respect to the peak maximum principal strain were obtained and are discussed.