Tensile and Shear Properties of Continuous Fiber‐Reinforced SiC/Al ₂ O ₃ Composites Processed by Melt Oxidation

Abstract

The mechanical properties of a fiber‐reinforced SiC/Al 2 O 3 composite have been investigated in tension and shear. The material is shown to have class II characteristics (a “matrix dominated” ceramic matrix composite) with appreciable inelastic strain prior to failure. This strain is associated with matrix cracking accompanied by interface debonding and sliding. One consequence of this strain is the ability to redistribute stress, resulting in tensile notch insensitivity . Evaluation of the interface properties from hysteresis measurements has indicated an interface slip resistance similar to that for SiC/CAS and debond behavior similar to that for SiC/SiC. The consequence is the occurrence of inelastic deformation at stress levels intermediate between those found for these other composites. The SiC/Al 2 O 3 has a relatively low initial modulus, because of cracking in the matrix‐only regions of the composite, caused by the thermal expansion mismatch between Al 2 O 3 and SiC. The ultimate tensile strength is consistent with global load‐sharing requirements.