Damage mechanism analysis to the carbon fiber and fiber-ceramic interface tailoring of Cf/ZrC-SiC using PyC coating

The damage mechanism of carbon fiber and fiber-ceramic interface of CarC-SiC were investigated and revealed. The chemical reactions of C with ZrO2 and SiO2 impurities during the sintering resulted in the surface and grain etching of fiber. The ZrC-SiC ceramics diffused into interface to form a strong bonding under high temperature and press, leading to a failure of stress release and guiding the crack propagation direct across fiber. Both consequently impeded the fiber pull-out and bridging. By obvious contrast, the chemical etching of fiber was effectively inhibited utilizing PyC coating as transition layer, and the strong bonding of fiber with ceramic was relieved at the same time replaced by a relatively weak bonding. As a result, the fiber pull-out and fiber bridging were boosted with a longer length more than 50 mu m, over 2 times of uncoated composite, accompanied with obvious crack branching and deflection, together resulting in a graceful mechanical feedback with 2.5 times of work of fracture and improved fracture toughness. This work not only revealed the microstructure forms and inherent mechanism on structure damage of carbon fiber, but also offered an effective method of protecting fiber and tailoring the interface bonding, thereby guiding the design of C-f/ZrC-SiC with graceful mechanical performance.