Effect of heat treatment on interface failure behavior in SiC_f/PyC/SiC composites reinforced with Cansas-3 fibers

The influence of heat treatment on the correlation between interfacial mechanical properties and microstructure in CVI-SiC_f/PyC/SiC composites was systematically investigated. The results reveal a progressive reduction in the average interfacial bond strength, interfacial shear stress, and interfacial debonding energy within the composites as the heat treatment temperature increases, especially beyond 1350 °C. This decline can be attributed to the attenuation of the SiC_f/PyC interfacial bond strength arising from the contraction in fiber volume induced by the precipitation of Cansas-3 fibers. After push-in testing, SiC_f/PyC/SiC composites heat-treated at or below 1350 °C displayed fibers in a compressed state. Conversely, composites exposed to extended heat treatment at 1400 °C or higher maintained fibers in an ejected state after push-in testing. Moreover, the composites heat-treated at 1450 °C and 1500 °C demonstrated fibers that were spontaneously ejected subsequent to cross-section polishing.