Mechanical properties and in situ crack growth observation of SiC/SiC composites

Continuous SiC fibre reinforced SiC matrix composites (SiC/SiC) have been studied as materials for high temperature and nuclear applications. In this work, 3D SiC/SiC composites with pyrolytic carbon (PyC) interface or carbon nanotubes (CNTs) interface were fabricated by polymer infiltration and pyrolysis (PIP) process, mechanical properties of the SiC/SiC composites were characterized and crack growth processes were observed in situ by SEM. The results indicated that the flexural strengths of both 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. The crack propagated along the fibre–matrix interface in the SiC/SiC composite with PyC interface, while the crack propagated rapidly through the fibres in the SiC/SiC composite with CNTs interface.