Microstructures,Strength and Toughness of 2D C_f/(C-SiC) Composites by Chemical Vapor Infiltration

Two dimensional carbon fiber-reinforced silicon carbide-carbon binary matrix composites(2D Cf/(SiC-C)) were fabricated by means of isothermal and isobaric chemical vapor infiltration(ICVI).The matrix structures of the 2D Cf/(SiC-C) composites were characterized by the backscattered electron imaging(BSE) of scanning electron microscope(SEM).Furthermore,their room temperature mechanical properties and fracture surfaces were compared with two dimensional carbon fiber-reinforced silicon carbide matrix composite(2D Cf/SiC).The results indicate that the matrices in the 2D Cf/(SiC-C) composites are multilayered structures composed of SiC and PyC layers.The PyC matrix layers are homogeneous and continuous,which are bonding well with SiC matrix layers.The 2D Cf/(SiC-C) composite with a thicker PyC matrix layer in fiber bundles exhibits better mechanical properties.Meanwhile,its tensile strength,failure strain,fracture toughness and fracture work are 3%,142%,22% and 58% higher than those of the 2D Cf/SiC composite,respectively.The multilayered matrices composed of SiC and PyC layers,cause the fibers in the 2D Cf/(C-SiC) composites to pull out twice in a concentrated mode.Moreover,the first pull-out fibers play a leading role in enhancing the strength and toughness.