Fatigue behavior and residual strength evolution of 2.5D C/C-SiC composites

The residual tensile strength (RTS) evolution of a chemical vapor infiltration and liquid silicon infiltration based 2.5 dimensional reinforced C/C-SiC (2.5D C/C-SiC) composites after fatigue loadings has been investigated. The results show that the fatigue limit (106 cycles) of the 2.5D C/C-SiC composites reaches 58.2 MPa, which corresponds to 75% of the virgin static tensile strength (77.7 MPa). Moreover, an ultimate strength enhancement is observed after fatigue loading. The most pronounced RTS increases to 92.5 MPa when specimens are subjected to fatigue stress of 69.3 MPa for 105 cycles. The microstructural analysis indicates that RTS after cyclic loading is affected by the formation and propagation of cracks and interfacial degradation. Furthermore, a model proposed in this work can well evaluate the RTS of the composites in relation to the number of the applied fatigue cycles.