Fabrication of sapphire fibre reinforced ceramic matrix composite

A combination of pressure filtration and reaction sintering techniques has been used for the fabrication of a fibre reinforced ceramic matrix composite. Large diameter (nominally 125 mu m) zirconia coated Saphikon monofilament sapphire fibre reinforcements were incorporated in a reaction sintered mullite matrix. Matrix formation was achieved by oxidation of beta silicon carbide to a cristobalite at 1250 degrees C and subsequent mullitisation with ex alumina at 1550 degrees C, optimisation of the matrix being achieved by study of the consolidation behaviour before fibre inclusion. Testbars exhibiting small dimensional changes after sintering have been produced with a relative density of approximately 96%. Young's modulus measurements were performed employing a forced resonance method in air and under vacuum. This testing method enabled changes in the elastic properties to be monitored in relation to matrix development during sintering, and with the addition of reinforcing fibres. The fracture behaviour of the composites was evaluated, and showed, to some extent, typical composite failure patterns.