Carbon-Carbon Composites – A Review

Abstract

Carbon-carbon composites (CCC) stand unique in the class of composites as they possess some extra-brilliant properties which the other composites do not have. They combine the advantages of both carbon fibre and carbon matrix such as high specific strength, stiffness and in plane toughness as well as refractory properties like retention of mechanical properties at extremely high temperatures of the order of 3000oC. This has resulted in the exploitation of CCC as structural materials in space vehicles, heat shields, rocket nozzles and aircraft brakes. Properties like biocompatibility and chemical inertness have led to new applications in medicine industry. Carbon fibres may be combined in a wide variety of forms; woven, knitted, braided and filament wound, to provide 1, 2 and multidirectional reinforced composites. The matrix can be a vapor deposited carbon, glassy carbon or coke. Also, the degree and extend of graphitization may be varied considerably, imparting a wide range of thermo-chemical properties of composites. Conventional fabrication techniques like Gas phase impregnation (Chemical vapour deposition (CVD)) and
Liquid phase impregnations were employed in the early ages of CCC fabrication. Later on, modifications like liquid phase pre-impregnation (LPI), hot pressing, hot isostatic pressure impregnation carbonization (HIPIC) and isothermal CVI saw the improvement in properties of the fabricated CCC. Advanced techniques like Preformed Yarn (PY) method showed exceptional values for specific strength and fracture toughness. Successful modifications and modern techniques like application of temperature, densification, increasing the number of pitch/resin impregnation cycles, using carbon nano tubes/carbon nano fibres as reinforcements, growing multi walled carbon nano-tubes on woven carbon fibre, fibre architecture modifications, microwave curing, fibre sizing, ultra-high temperature ceramic coating are also reviewed to throw light on how these have improved the important mechanical properties, which make CCC as the “material of future”.