Effects of SiC content on the mechanical and thermophysical properties of 3D C_f/SiC–Al composites

Abstract

3D C_f/SiC–Al composites were achieved through the pressure infiltration of liquid Al–Si alloy into porous 3D C_f/SiC preform, which was produced by different cycles of precursor infiltration and pyrolysis. The effect of silicon carbide volume fraction on the microstructure, anisotropic mechanical response, and thermophysical characteristics of the 3D C_f/SiC–Al composites was investigated. The results demonstrated that the initial microstructure of 3D C_f/SiC can be retained, and the obtained C_f/SiC–Al composites presented remarkable anisotropy characteristics. As the silicon carbide ceramics content increased from 12.5 vol% to 41.8 vol%, the thermal conductivity and thermal expansion coefficient of 3D C_f/SiC–Al composites decreased, whereas the bending strength initially increased and then decreased in the Z-direction. The bending strength perpendicular (Z) to the carbon cloth layer of 3D C_f/SiC–Al composites was higher than that of parallel (X–Y) to the carbon cloth layer. However, a significant anisotropy in the thermal conductivity values was the opposite. The 3D C_f/SiC–Al composite with 1ow ceramic content (17 vol%) had a higher thermal conductivity in the X–Y direction (64 W m⁻¹ K⁻¹) than in the Z-direction (34 W m⁻¹ K⁻¹). The thermal expansion coefficient of all the 3D C_f/SiC–Al composites along the X–Y direction also decreased initially and then increased in the range of 100–450 °C, which presents low expansion characteristics.