Fibrous composites with high melting-point matrices

Abstract

It is now well established that the strength and stiffness of materials such as epoxy resins and aluminium can be increased by the incorporation of suitable fibres. However, relatively little effort has been made to improve similarly the high temperature strength of materials intended for service above ca . 800°C. This paper is introduced with a general examination of fibre/matrix systems that offer improved high temperature capability over current materials, with reference to gas turbine blade applications. The importance of properties and characteristics that influence the selection of suitable fibre and matrix combinations, for example, density, strength, oxidation resistance and compatibility, are discussed. Experi­mental work on the strength of potentially useful fibres such as refractory metal and alumina filaments, their incorporation into nickel-base alloy matrices using vacuum-casting techniques, and the evaluation of composites are described. In terms of the measured properties and of strength predictions based on fibre and matrix data, the merits and limitations of composites relative to well-developed alloys strengthened by precipitation mechanisms are considered.