Effect of PyC interphase thickness on mechanical behaviors of SiBC matrix modified C/SiC composites fabricated by reactive melt infiltration

Abstract

A dense carbon fiber reinforced silicon carbide matrix composites modified by SiBC matrix (C/SiC-SiBC) was prepared by a joint process of chemical vapor infiltration, slurry infiltration and liquid silicon infiltration. The effects of pyrolytic carbon (PyC) interphase thickness on mechanical properties and oxidation behaviors of C/SiC-SiBC composites were evaluated. The results showed that C/SiC-SiBC composites with an optimal PyC interphase thickness of 450nm exhibited flexural strength of 412MPa and fracture toughness of 24MPam1/2, which obtained 235% and 300% improvement compared with the one with 50nm-thick PyC interphase. The enhanced mechanical properties of C/SiC-SiBC composites with the increase of interphase thickness was due to the weakened interfacial bonding strength and the decrease of matrix micro-crack amount associated with the reduction of thermal residual stress. With the decrease in matrix porosity and micro-crack density, C/SiC-SiBC composites with 450nm-thick interphase exhibited excellent oxidation resistance. The residual flexural strength after oxidized at 800, 1000 and 1200°C in air for 10h was 490, 500 and 480MPa, which increased by 206%, 130% and 108% compared with those of C/SiC composites.