DEVELOPMENT OF ALUMINIUM ALLOY BASED CARBON FIBRE REINFORCED METAL MATRIX COMPOSITES

Abstract

Fibre reinforced metal matrix composites (FMMCs), are a new range of advanced engineering materials used mainly at elevated temperatures where existing materials are not suitable for use. The FMMCs can be tailored to produce various combinations of stiffness and strength. The FMMCs are generally anisotropic, but show very high strength and modulus along the direction of fibre alignment. When costly fibres are reinforced in metal matrices by relatively costlier processing route of powder metallurgy and diffusion bonding, then very expensive FMMCs are produced. These can only be used in aerospace and military industries as these industries offer a large premium on weight saving. Aluminium and its alloys when reinforced with low cost and low density carbon fibres, by relatively economical solidification processing route, produce cheap FMMCs having specific strength and specific modulus far superior to those of steels. Therefore, aluminium-carbon fibre (A1/CF) composites may have a high potential to be used even in automotive industries where premium on weight saving is very less as compared to aerospace and military industries. Carbon fibres are poorly wetted by aluminium and its alloys at low temperatures and aluminium reacts with carbon fibres at high temperature resulting in poor infiltration and degraded fibres respectively. The problem of poor wettability can be solved by adding sufficient amounts of surface active or reactive elements to aluminium, whereas the degradation of fibres can be minimised by using squeeze casting technique for the solidification synthesis of the AUCF composite. Thus, it is possible to reinforce the carbon fibres uniformly by the solidification processing in aluminium alloy matrices without substantial degradation of fibres.