LONG-FIBER REINFORCED METAL-MATRIX COMPOS ITES

Continuous fibre reinforced metal matrix composites are candidates for several aeronautical and space applications. This paper surveys and o utlines the main materials and manufacturing routes developed currentl y for their production. Some mechanical properties are also described. The recent availability of high performance fibres has provoked a ren ewal in activity related to the study and development of long fibre re inforced metal matrix composites. These composites exhibit much improv ed properties, in terms of specific strengths and stiffness at room an d elevated temperatures, compared to unreinforced structural materials . This article attempts a review concerning SiC-reinforced titanium, c arbon- and alumina-reinforced aluminium and magnesium matrix composite s. For SiC-fibre reinforced titanium composites, the fabrication proce sses have been thoroughly investigated, a bulky database on mechanical properties is available and industrial applications are under way, su ch as reinforcement of compressor disks in aeronautical turbine engine s. However, for applications at higher temperatures, other matrix allo ys must be envisaged, such as intermetallics materials and several pro blems, such as the interphase optimisation, are still to be addressed. In the case of aluminium or magnesium matrix composites, reinforced w ith carbon or alumina fibres, the infiltration process under moderate pressure (10-20 MPa) has proven to be the most viable for fabricating components having complex geometries. Recent works on the adaptation o f the process and on the selection of the constituents (fibres, alloy with appropriate heat treatment, fibre coating if necessary) have demo nstrated the potentialities of these materials. For example, unidirect ional carbon reinforced aluminium composites displaying tensile streng ths over 1800 MPa have been produced. The low transverse strength of t hese material can be alleviated by the use of multidirectional reinfor cements. Accompanying studies are now required to understand and model the properties of these composites, in particular their mechanical be haviour and corrosion resistance.