Microstructure and mechanical properties of SiCP/SiC and SiCW/SiC composites by CVI

37.2 vol.% SiCP/SiC and 25.0 vol.% SiCW/SiC composites were prepared by chemical vapor infiltration (CVI) process through depositing SiC matrix in the porous particulate and whisker preforms, respectively. The particulate (or whisker) preforms has two types of pores; one is small pores of several micrometers at inter-particulates (or whiskers) and the other one is large pores of hundreds micrometers at inter-agglomerates. The microstructure and mechanical properties of 37.2 vol.% SiCP/SiC and 25.0 vol.% SiCW/SiC composites were studied. 37.2 vol.% SiCP/SiC (or 25.0 vol.% SiCW/SiC) consisted of the particulate (or whisker) reinforced SiC agglomerates, SiC matrix phase located inter-agglomerates and two types of pores located inter-particulates (or whiskers) and inter-agglomerates. The density, fracture toughness evaluated by SENB method, and flexural strength of 37.2 vol.% SiCP/SiC and 25.0 vol.% SiCW/SiC composites were 2.94 and 2.88 g/cm3, 6.18 and 8.34 MPa m1/2, and 373 and 425 MPa, respectively. The main toughening mechanism was crack deflection and bridging.