Flexural fatigue behavior and residual strength evolution of SiCnws-C/C composites

The flexural fatigue behavior and residual flexural strength evolution of SiC nanowires reinforced carbon/carbon (SiCnws-C/C) composites were investigated. Specimens were loaded at a stress level of 65% of their static flexural strength for 10⁵, 5 × 10⁵ and 10 × 10⁵ cycles, and their residual flexural strength was increased by 4.87%, 13.73% and 62.45% respectively after cyclic loading. Results indicate that the residual strength after cyclic load is affected by the formation and propagation of cracks, interfacial degradation, as well as the relief of residual thermal stress. An appropriate interfacial debonding and releasing of residual thermal stress are responsible for the large improvement of residual strength of SiCnws-C/C composites after 10 × 10⁵ fatigue cycles. Compared with carbon/carbon composites, SiCnws-C/C composites demonstrate higher mechanical strength and stronger resistance to crack propagation, which are ascribed to the strengthening effect brought by the SiC nanowires, including their pull-out, breaking and bridging.