Cyclic fatigue behavior of carbon fiber-reinforced ceramic-matrix composites at room and elevated temperatures with different fiber preforms

In this paper, the cyclic fatigue behavior of unidirectional, cross-ply, 2D, 2.5D and 3D C/SiC composites at room and elevated temperatures has been investigated. The fatigue life S-N curves, fatigue hysteresis modulus, fatigue hysteresis dissipated energy and interface shear stress versus cycle number curves have been analyzed. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of the preforms. The fatigue limit, the degradation rate of fatigue hysteresis dissipated energy and interface shear stress are highest for unidirectional C/SiC with the highest ECFL, and lowest for 2.5D C/SiC composite with the lowest ECFL. At the same fatigue peak stress level and interface shear stress, the fatigue hysteresis dissipated energy of 2D and 2.5D C/SiC composites are much higher than that of unidirectional and cross-ply C/SiC composites due to low ECFL and fibers bending inside of composites.