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The use of silicon carbide-type fibres to reinforce lithium aluminosilicate glass ceramics results in composites with exceptional levels of strength and toughness. It is demonstrated that composite strength and stress-strain behaviour depend on in situ fibre strength, matrix composition, test technique and atmosphere of test. Both linear and non-linear tensile stressstrain curves are obtained with ultimate strengths at 22 ~ C approaching 700 MPa and failure strains of 1%. Flexure tests performed at up to 1000~ in air are compared with data obtained in argon to demonstrate a significant dependence of strength and failure mode on test atmosphere. Finally, glass ceramic matrix composite performance is compared with a silicon carbide fibre-reinforced epoxy system to demonstrate the importance of matrix failure strain on strength and stress-strain behaviour.

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Silicon carbide fibre-reinforced glass-matrix composites have been fabricated and tested. Two fibre forms, a 140/~m diameter monofilament and a 10/~m diameter filamentary yarn, were incorporated into a matrix of borosilicate glass. The hot-pressing fabrication procedure resulted in fully dense unidirectionally reinforced specimens with excellent flexural strength and fracture toughness over the temperature range 22 to 700 ~ C. In addition, composite thermal expansion was found to be nearly independent of fibre orientation indicating that multiaxially reinforced composites should be readily fabricable without the occurrence of extensive cracking.