Mechanical properties of SiCf/SiC composites with PyC and the BN interface

Abstract

To tailor the fibre–matrix interface of continuous-silicon-carbide-fibre-reinforced silicon carbide (SiCf/SiC) composites for improved mechanical properties, SiC fibres were coated with pyrolytic carbon (PyC) and BN interfaces using chemical vapour deposition (CVD) and the dip-coating process, and three-dimensional SiCf/SiC composites with such interfaces were fabricated using the precursor infiltration and pyrolysis (PIP) process. The microstructures of the SiC fibres with different coatings were characterised using a scanning electron microscope. The effects of the coating processes on the tensile strengths of the SiC fibres were studied using a single-filament tensile strength test. The mechanical properties of the SiCf/SiC composites were evaluated using the three-point bending test and single-edged notch beam test. The results indicate that the SiC fibres with single-layer PyC coating have larger single-filament tensile strengths than the original fibres. The SiCf/SiC composites with a single-layer PyC coating as an interface exhibit an optimal mechanical property. The average flexural strength and fracture toughness of the single PyC-coated composites were 433.1MPa and 20.0MPam1/2, respectively.