Oxide-fibre/Ni-based matrix composites—III: a creep model and analysis of experimental data

Abstract

Recent results of creep and creep-rupture experiments with oxide-fibre/Ni-based-matrix composites at temperatures of 1100–1200 °C clearly showed a need to use adequate models of the creep behaviour of composites to enable their behaviour to be analysed appropriately. In the present paper, a new creep model for a composite with creeping matrix and initially continuous brittle elastic fibres is developed. The model accounts for fibre breakage in the transitional stage of creep and steady-state conditions are found by evaluating an average fibre length that cannot be divided into shorter segments. The model allows analysis of the dependence of composite creep rate on such composite microstructure parameters as statistics of the fibre strength, creep characteristics of the matrix, and the fibre/matrix interface strength. Comparison of calculated results with experimental behaviour shows the applicability of the model to computer simulation of the creep behaviour of heat-resistant composites as well as to optimising the composite microstructure. Combining the experimental data with results of calculations evaluates both present and future potentials of oxide-fibre/Ni-based-matrix composites. Composite specimens obtained and tested up to now show the possibility of their application as heat-resistant materials up to a temperature of 1150 °C. The maximum use temperature can be essentially enhanced provided a better fibre/matrix bonding has been achieved.