Response of SiC/Ti under combined loading Part III: Microstructural evaluation

A post-failure microstructural evaluation of unidirectional [0₄] and angleply [±45], silicon carbide/titanium (SiC/Ti) tubular specimens that were tested under multiaxial loading is presented. This evaluation indicates that damage is concentrated near the fiber/matrix interface. Radial interface cracks and debonding as well as plastic slip in the matrix were observed in the [0₄] tubes. In addition to the presence of interfacial debonding in the as-fabricated condition, the [±45], tube was observed to contain much more damage and plastic deformation after mechanical loading than the [0₄] tubes. Transverse fiber cracks and isolated areas of matrix cracking were also observed in the [±45], tubes. The observed permanent deformation mechanisms are consistent with measured strains. A micromechanical model has been used to predict the evolution of damage and matrix plasticity for the loadings applied in the experimental program. The theoretical predictions are consistent with observed permanent deformation mechanisms.