Interfacial sliding in multi-component material systems and its mechanism

Large shear stresses may develop at interfaces between dissimilar materials during thermomechanical excursions when there is a significant difference in the coefficient of thermal expansion (CTE) between them. Most typically, these shear stresses are confined to the extremities of one of the components, such as fiber-ends in a composite, or the edges of a thin film on a substrate. However, when the dimensions of the phases are small, these shear stresses may prevail over a large area fraction of the total interface. Under appropriate thermal-mechanical conditions, the interface may slide via diffusional processes, thereby accommodating relative dimensional changes between the phases. In this paper, we present evidence of interfacial creep in metal-matrix composites, thin-films on substrates, and interconnect structures in microelectronic devices. Experiments for determining the kinetics and mechanism of this phenomenon are also presented, along with an approach for modeling the impact of this phenomenon in continuous fiber reinforced metal-matrix composites.