Microstructure and mechanical properties of SiCf/SiC composite prepared by chemical vapor infiltration

Abstract

Continuous silicon carbide (SiC) fiber reinforced SiC ceramic matrix (SiCf/SiC) composites are widely studied for possible applications as hot sections in next-generation aeroengines because of their excellent thermo-structural properties. Their mechanical properties were comprehensively evaluated based on the interaction mechanisms among fiber, interphase, and matrix. Moreover, it was found that matrix cracking and fiber bridging mechanisms influenced the shear-dominated and tension-dominated properties, respectively, clearly indicating that the mechanical properties of the material should be correlated. In this study, mechanical properties of the two-dimensional SiCf/SiC composite were comprehensively evaluated, and the correlation laws were verified between tension and bending, tension and in-plane shear, and in-plane shear and interlaminar shear. Results showed that the ratio of shear to tensile matrix cracking stress was 0.68, while the ratio of flexural to tensile strength was 2.3, and the interlaminar shear strength was equal to the in-plane shear strength minus the fiber bridging stress. Fiber bridging is the key mechanism controlling the above-mentioned correlation by the established meso-mechanical formulas, and the interlaminar shear mechanism is controlled by matrix cracking and influenced by interlaminar pores.