Fracture Behavior of SiC/SiC Composites with Different Interfaces

SiC fiber reinforced SiC matrix composites (SiC/SiC) are promising materials for high temperature structural applications. In this work, SiC/SiC composites with Pyrolytic Carbon (PyC) interface or Carbon Nanotubes (CNTs) interface were fabricated by polymer infiltration and pyrolysis (PIP) process. Overall mechanical properties and interfacial shear strength of the SiC/SiC composites were characterized and crack growth processes were observed in situ by scanning electron microscope (SEM). The results indicate that flexural strengths of two types of SiC/SiC composites are similar, but the fracture toughness of the SiC/SiC composite with PyC interface is twice as much as that of the SiC/SiC composite with CNTs interface. Cracks propagate along the fibre-matrix interface in the SiC/SiC composite with PyC interface, which can be deflected or arrested by the PyC interface, hence the composite exhibits a pseudo-ductile fracture behavior. However, the CNTs interface fails to cease the crack in the SiC/SiC composite with CNTs interface, so the initial crack propagates rapidly through the fibers leading to final main crack, and a brittle fracture mode.