Microstructure and high temperature strength of SiCW/SiC composites by chemical vapor infiltration

SiCW/SiC composites without an intergranular glassy phase are prepared by the CVI process. The microstructure and high temperature strength of SiCW/SiC composites are investigated. The high temperature strength of SiCW/SiC composites depends on the interfacial bonding strength between matrix and whiskers. The matrix is effectively strengthened and toughened by the whiskers, and SiCW/SiC composites show a constant strength of 475 ± 32 MPa below 1000 °C. The flexural strength gradually declines from 475 ± 32 MPa to 208 ± 15 MPa at the temperature from 1000 °C to 1500 °C due to the decreased whisker-matrix interfacial bonding strength. The interfacial bonding strength is too low to transfer stress from the matrix to the whiskers, and SiCW/SiC composites show a constant strength of 208 ± 15 MPa at temperatures from 1500 °C to 1800 °C. The fracture mode of SiCW/SiC composites changes from the toughened fracture below 1000 °C to the brittle fracture above 1000 °C.