Interface Damage of Ceramic-Matrix Composites

Abstract

Under cyclic fatigue loading, the damage mechanisms of fiber/matrix interface debonding, interface sliding and interface wear degrade the fiber/matrix interface shear stress. The fiber/matrix interface shear stress plays an important role in the fatigue behavior of fiber-reinforced ceramic-matrix composites (CMCs). In this chapter, the fiber/matrix interface shear stress of fiber-reinforced CMCs with different fiber preforms, i.e., unidirectional, 2D cross-ply and woven, 2.5D woven and 3D braided, is estimated from the fatigue hysteresis dissipated energy at room and elevated temperatures. The experimental fatigue hysteresis dissipated energy versus the applied cycles and the theoretical fatigue hysteresis dissipated energy versus the fiber/matrix interface shear stress relationship are analyzed. With decreasing fiber/matrix interface shear stress, the fatigue hysteresis dissipated energy increases to the peak value, and then decreases to zero, corresponding to the fiber/matrix interface slip Case I, II, III, and IV. Using the experimental fatigue hysteresis dissipated energy, the fiber/matrix interface shear stress of unidirectional SiC/CAS, SiC/Si₃N₄ with the strong and weak fiber/matrix interface bonding, C/SiC at room temperature and 800 °C in air condition, cross-ply SiC/CAS and C/SiC at room temperature, 700, 800, and 850 °C in air condition, 2D C/SiC at room temperature, 550 °C in air and 1200 °C in vacuum conditions, 2D SiC/SiC at room temperature, 800 °C in air, 600, 800, and 1000 °C in inert, 1000, 1100, and 1200 °C in air and steam, 1300 °C in air conditions, 2.5D C/SiC at room temperature, 800 °C in air and 600 °C in inert conditions, and 3D braided SiC/SiC at 1300 °C in air conditions are obtained.