Synthesis of Polycarbosilane, Polymer Impregnation Pyrolysis based C SiC Composites and Prototype Development

Due to some extraordinary thermo-mechanical properties, silicon carbide is considered one of the best materials used for high temperature applications in defence and aerospace. Polycarbosilane (PCS) has been widely used as SiC precursor. This paper describes the research and development work undertaken to establish the technologies for synthesis and characterisation of PCS, fabrication process and characterisation of Carbon fibre reinforced SiC matrix (C/SiC) composite laminates and shaped articles. The molecular weight and softening point of the PCS was found to be 1400-1800 Mn and 140-150 °C respectively. Flexural stress of the unidirectional (UD) C/SiC composites and bidirectional (2D) C/SiC composites was found to be 400-450 MPa and 300-350 MPa respectively. Tensile stress of the 2D C/SiC composite was found to be around 200 MPa. Coefficient of thermal expansion and thermal diffusivity of the 2D C/SiC composites at RT- 1000 °C were found to be in range of 0.3-2.2×10-6/ °C and 32-6 mm2/s respectively. The fabrication process developed for the UD and 2D C/SiC composites using the indigenous PCS has been also demonstrated to fabricate typical size divergent rocket nozzle and hot structure. Fabrication process of the SiC fibre has also been described in brief