FINITE-ELEMENT MODELING OF CREEP DEFORMATION IN FIBER-REINFORCED CERAMIC COMPOSITES

The tensile creep and creep-recovery behaviour of a unidirectional SiC fibre-Si3N4 matrix composite was analysed using finite element techniques. The analysis, based on the elastic and creep properties of each constituent, considered the influence of fibre-matrix bonding and processing-related residual stresses on creep and creep-recovery behaviour. Both two- and three-dimensional finite element models were used. Although both analyses predicted similar overall creep rates, three-dimensional stress analysis was required to obtain detailed information about the stress state in the vicinity of the fibre-matrix interface. The results of the analysis indicate that the tensile radial stress, which develops in the vicinity of the fibre matrix interface after processing, rapidly decreases during the initial stages of creep. Both the predicted and experimental results for the composite show that 50% of the total creep strain which accumulated after 200 h at a stress of 200 M Pa and temperature of 1200-degrees-C is recovered within 25 h of unloading.