Oxidation effects on in-plane and interlaminar shear strengths of two-dimensional carbon fiber reinforced silicon carbide composites

Effects of oxidation on in-plane shear strength and interlaminar shear strength of two-dimensional carbon fiber reinforced silicon carbide composites (2D C/SiC) were studied based on the corresponding shear damage mechanisms. The results showed that oxidation had resulted in severe degradations of the two strengths, however, it had little influence on the shear failure mechanisms. Under in-plane shear loading, large-scale fiber bridging mechanism controlled the shear behaviors. A modified rigid body sliding model was proposed to characterize the in-plane shear strength. In Comparison, interface sliding mechanism controlled the interlaminar shear strength. Based on above failure mechanisms, the two shear strengths were quantitatively characterized by the constituent properties, such as diameter of carbon fibers, interface sliding stress, matrix fracture energy and matrix cracking spacing. Therefore, oxidation effects on them were attributed to the decreased constituent properties which mainly results from oxidation consumption of the carbon phases. Finally, for the conditions of this study, a relationship was proposed that the interlaminar shear strength equals the in-plane shear strength minus the fiber bridging stress.