Creep behavior of interfaces in fiber reinforced metal–matrix composites

Abstract

The elevated temperature deformation behavior of interfaces in model single fiber composites was isolated and studied using a fiber push-down approach, whereby the interface is loaded in shear. Two fiber–matrix systems, one with no mutual solubility (quartz–lead) and the other with limited mutual solubility (nickel–lead), were investigated. In both systems, the matrix and fiber underwent sliding relative to each other, with the interface acting as a high diffusivity path. The mechanism of sliding was inferred to be interface-diffusion-controlled diffusional creep with a threshold stress (Bingham flow). The behavior was modeled analytically using a continuum approach, and an expression for the constitutive creep behavior of the interface was derived. The model provided a physical basis for the observed threshold behavior, which was found to be directly related to the normal (radial) residual stress acting on the fiber–matrix interface. The results are deemed to be significant because: (1) in some instances, interfacial sliding may be instrumental in determining the overall creep/thermal cycling response of a composite; and (2) they offer an alternative rationalization of threshold behavior during diffusional flow (besides interface reaction control) and may be useful in understanding creep in multi-phase systems with internal stresses.