High-temperature flexural properties of SiBC modified C/SiC composites

In the present paper, high-temperature flexural properties of the SiBC modified C/SiC composites were investigated via the four-point bending method. The flexural strength and elastic modulus of the composites tested at 25 °C, 800 °C and 1200 °C were 276 MPa, 377 MPa, 440 MPa, and 78 GPa, 183 GPa, 189 GPa, respectively. As temperature increase, thermal residual stress is released gradually, and the matrix micro-cracks and defects decrease, leading to the enhanced high-temperature elastic modulus. Interface bonding strength increases due to the gradually thermal match between the fiber and matrix, which guarantees that load could be effectively transferred from the matrix to the fiber. Therefore, the composites show higher flexural strength at high temperatures than that at room temperature. When the composites were fractured at 1200 °C, the long pull-out fiber was observed, consistent with the high flexural strength of the composites.