MICROSTRUCTURE AND MECHANICAL PROPERTIES OF C/C-SIC COMPOSITES REINFORCED WITH FIBERS TREATED AT ELEVATED TEMPERATURES

C/C-SiC composites fabricated via liquid silicon infiltration are potential materials for the applications of high temperature technologies. However, the microstructure features and mechanical properties of C/C-SiC composites can be modified by heat treatment of carbon fibers. In the current work, in order to investigate the influence of carbon fiber heat treatment on the mechanical properties of C/C-SiC composites, the carbon fiber was treated at elevated temperatures under nitrogen atmosphere. The fracture toughness and interlaminar shear strength were evaluated by means of single edge notched-beam and double notch shear tests, respectively. The microstructure of C/C-SiC composites before and after mechanical testes was observed by scanning electron microscopy. Combining the mechanical properties with microstructure analysis, it was found that the heat treatment of carbon fiber could effectively change the mechanical properties: (i) a moderate treatment temperature could improve the fracture toughness of composite; (ii) the ILSS of composite increased with increasing the treatment temperature of carbon fiber. The high interlaminar shear strength of composite reinforced with treated fibers could be attributed to the large volume fraction of SiC matrix, strong fiber/matrix interface bonding and its homogeneous distribution.