Mechanical properties of short oxide fibre-kaolin clay matrix composites

A series of short fibre ceramic composites was produced by mixing, slip casting, and sintering kaolin clay with Al₂O₃ or mullite fibres at various volume contents. Sintering was conducted in air at various temperatures. The resulting composites were characterised with respect to chemical and mineralogical composition, microstructure, and mechanical properties. Sintering above 1200 °C changed the microstructure of kaolin from a weak point bonded structure to a strong dense glass ceramic structure, and changed δ-Al₂O₃ to α-Al₂O₃. The addition of oxide fibres to kaolin clay resulted in the formation of ceramic matrix composites, the properties of which depended on sintering temperature, matrix and fibre structures and relative volumes, the properties of the fibre/matrix interface, and fibre length. A relative increase in strength and toughness with incorporation of fibres is achieved with limited additions of fibres, and mainly in the weak point bonded structures. The application of linear elastic fracture mechanics to the examined ceramic matrix composites is also discussed.