Model-neutron diffraction strain measurement comparisons for steady state creep of metal matrix composites

Mori and coworkers have developed a model for the prediction of the steady state creep rate of discontinuous composites based on the Eshelby model. This model recognizes that matrix creep can only achieve steady state creep when relaxation processes at the inclusion/matrix interface balance the rate of build up of internal stress. In this paper we follow through the implications of this model for the level of the average matrix stress attained in the steady state as a function of the applied load. We compare the predictions with direct measurements of the matrix stress by neutron diffraction. The model indicates that the composite creep exponent should be less than the creep exponent of the unreinforced matrix provided neither debonding nor inclusion cracking occurs. This is observed experimentally for the composites under the conditions studied.