Polycarbosilane based UD C/SiC composites: Effect of in-situ grown SiC nano-pins on mechanical properties

Uni-directional C/SiC composites were fabricated by thermal molding of carbon fiber tows with the in-house synthesized polycarbosilane. The molding was carried out at 300 °C followed by pyrolysis at two different temperatures viz. 1400 and 1600 °C. The composite specimens were densified by repeated vacuum infiltration of the polycarbosilane at 170 °C and pyrolysis at the pre-decided temperatures to achieve density up to 1.8–1.85 g/cc. Flexural and tensile strength of the composites pyrolysed at 1600 °C were found to be 700 MPa and 275 MPa while the properties of the composites pyrolysed at 1400 °C were about 20% lower than these values. Micro-structure revealed that the in-situ growth of SiC nano-pins at 1600 °C, play an important role to enhance the mechanical properties. Growth mechanism of the SiC nano-pins has also been proposed.