Room- and elevated-temperature mechanical properties of SiC fiber-reinforced SiC composite fabricated by CVI and PIP methods

The three-point bending strength of two-dimensional SiC fiber-reinforced SiC composites (SiC/SiCf) fabricated by chemical vapor infiltration (CVI) method and polymer infiltration and pyrolysis (PIP) method was measured at room and high temperatures up to 1600 degrees C and the fracture behavior was investigated, The maximum strength of the CVI-SiC/SiCf composite with carbon-coated Hi-Nicalon cloth was maintained at around 200 MPa up to 1600 degrees C. The fracture behavior of the CVI-SiC/SiCf composite showed non-brittle characteristics with fiber pull-out up to 1500 degrees C, whereas it showed brittle fracture at 1600 degrees C. On the other hand, the maximum strength of the PIP-SiC/SiCf composite increased gradually from 40 to 70 MPa with increasing test temperature, due to the crystallization of the matrix. The PIP-SiC/SiCf composite with carbon-coated Hi-Nicalon had higher strength and fracture energy than that with non-coated Hi-Nicalon. The PIP-SiC/SiCf composite with carbon-coated Hi-Nicalon showed non-brittle fracture up to 1400 degrees C, whereas that with non-coated Hi-Nicalon showed almost brittle fracture at room and high temperatures, except at 1400 degrees C. The PIP-SiC/SiCf composite significantly differed from the CVI-SiC/SiCf composite in maximum strength. This could be mainly explained by bulk density.