Development of non-brittle fracture in SiCf/SiC composites without a fiber/matrix interface due to the porous structure of the matrix

Silicon carbide (SiC) porous-matrix composites lacking a fiber/matrix interface and incorporating continuous unidirectional SiC fibers as reinforcements were developed using sandwiched layers with non-infiltration fiber bundles and a porous matrix in a laminate to achieve crack deflection. Excellent control of the porosity was achieved by varying the amount of carbon powder added. The matrix porosity was characterized in terms of its microstructure and mechanical properties. The SiC porous-matrix composite with an open porosity of 22%, which was formed with 40 vol% carbon powder, had a flexural strength of 253 ± 31 MPa and exhibited non-brittle fracture behavior up to a stress maximum, followed by a gradual depletion of the fracture energy, decreasing the stress on continued deformation. Significant changes in the mechanical properties, such as the flexural strength and fracture energy, of the fabricated SiC porous-matrix composite were not observed following exposure to air at high temperature (up to 1100 °C).