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 C_f/(SiC-C)) were fabricated by means of isothermal and isobaric chemical vapor infiltration (ICVI). The matrix structures of the 2D C_f/(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 C_f/SiC). The results indicate that the matrices in the 2D C_f/(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 C_f/(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 C_f/SiC composite, respectively. The multilayered matrices composed of SiC and PyC layers, cause the fibers in the 2D C_f/(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.