The influences of carbon nanotubes introduced in three different phases of carbon fiber/pyrolytic carbon/silicon carbide composites on microstructure and properties of their composites

The influences of carbon nanotubes (CNTs) introduced in three different phases of carbon fiber/pyrolytic carbon/silicon carbide (Cf/PyC/SiC) composites on the microstructure and properties of the composites were investigated in this paper. The results showed with CNTs introduced at PyC-PyC interface, tensile strength and work of fracture (WOF) of a Cf/PyC/SiC composite had the largest increase, and significantly improved 54.9% and 130.3% respectively from those of the CNTs-free composite. Multiple interfaces (CF-PyC interface, CNT-PyC interface, PyC-PyC interface) failure and a great number of carbon fiber and carbon nanotube pull-outs were observed from tensile fracture morphology of the composite, which indicated weakening of PyC-PyC interface due to CNTs and accounted for the remarkable improvement in WOF of the composite. The increase of tensile strength of the composite was resulted from the reduction of residual stress of the composite.