The Effect of PyC/SiC Compound Interphase on the Properties of PIP SiC/SiC Composite

Abstract In order to improve the properties of SiC/SiC composite, chemical vapor infiltration (CVI) process was applied for fabricating the PyC/SiC compound interphase. Precursor infiltration and pyrolysis (PIP) process was used to fabricate SiC matrix. Then an investigation was carried out for the effect of PyC/SiC compound interphase thicknesses on the properties of the composites. According to the results, it was found that the mechanical properties of composites with the PyC/SiC compound interphase are much higher than those of composite with only PyC interphase. The flexural strength, flexural modulus, fracture toughness and interlaminar shear strength of the composites increase gradually when the thickness of CVI SiC interphase is lesser than 2 μm. Further increase of the thickness of CVI SiC interphase to 4μm leads to a continuous increase on the modulus of the composites, while a decrease trend occurs on the flexural strength, fracture toughness and interlaminar shear strength of the composites because of the different coefficients of thermal expansion of the CVI SiC interphase and the PIP SiC matrix. SiC/(PyC/SiCx)/SiC composites showed the better properties of oxidation resistance than those of SiC/PyC/SiC composite. It was due to the survived PyC interphase protected by CVI SiC interphase when the oxygen diffuses into the compound PyC/SiCx intherphase.