A finite element method analysis of the role of interface behavior in the creep rupture characteristics of a discontinuously reinforced composite with sliding grain boundaries

In this study, the role of interfacial behavior in the creep cavitation and rupture characteristics of a discontinuously reinforced composite is investigated by using the finite element method and the results are compared with the results obtained for an unreinforced polycrystalline matrix material having identical grain morphology. Free sliding of the grain boundaries, a continuous nucleation of the grain boundary cavities, their diffusional growth and coalescence to form grain boundary facet cracks are fully accounted for in the analyses. Although the composites having failure at the interface exhibited significantly lower minimum creep rates, their rupture time could be as short as or even shorter than that seen for the unreinforced polycrystalline matrix material. In contrast with the behavior of polycrystalline matrix material, in composites after the formation of the first facet crack, resulting from the coalescence of cavities, a significant time is required for the formation of the other grain boundary facet cracks across the ligament to cause final rupture. Therefore, the life predictions based on the models of cavity coalescence on a single grain boundary facet or interfacial debonding will significantly underestimate the composite creep life.