Deformation and failure processes during tensile creep of fibre and whisker reinforced SiC/Al2O3 composites

The tensile creep and creep fracture properties in air from 1473 to 1673 K are reported for an alumina matrix composite, reinforced with interwoven bundles of silicon carbide (Nicalon™) fibres aligned parallel and normal to the stress axis. The creep strength of this 0/90° SiCf/Al2O3 composite is determined by the longitudinal fibres, with creep of the fibres accompanied by crack development in the weak porous matrix. Oxygen penetration then promotes failure of the fibres bridging the developing cracks, with creep fracture occurring when a crack becomes long enough to cause sudden failure by fibre pull-out. These behaviour patterns are discussed in relation to tensile creep data available for SiC whisker-reinforced alumina, allowing comparisons to be made between the effects of whisker and fibre reinforcement on the high-temperature creep and creep fracture characteristics of SiC/Al2O3 composites.