Creep investigations of alumina-based all-oxide ceramic matrix composites

The long-term tensile creep behavior of all-oxide ceramic matrix composites (CMCs) was investigated. The accompanying fiber bundle tests revealed a strong influence of processing conditions on the creep resistance. CMCs with perpendicular fiber orientations were tested under two different load directions, moreover CMCs with nearly unidirectional fiber texture were investigated. Depending on the conditions, the absence of a steady-state creep stage was observed in most cases and due to an early onset of damage. As the majority of the samples was tested up to high strains and rupture, different failure mechanisms could be evaluated. An attempt was made to estimate fiber controlled creep rates via bundle data, but this approach also revealed problems when elastic data from unidirectional composites are transferred to CMCs with more complex fiber architecture.