An interface is formed when a minimum of two parts are in contact. Loading of the interface occursat the contact patch, which ranges in dimension depending on the contact geometry. The contact patch is the apparent area of contact of the two surfaces; multiple contact patches may exist on a given interface. The input load on the interface can be grouped into two categories - static and dynamic. In the static case, the loads on the contact patch are known a priori and do not change with time. In the dynamic case, commonly observed in structural dynamics interfaces, the load at the interface varies dynamically. In both cases, the surface topology, and local material properties(Elastic Modulus, etc) of the interface change in response to several variables including: loading of the interface, geometry of the interface, and the density of the local contact patches in contact region. Recent experiments conducted at several Joint Mechanics summer research programs from 2015 through 2018, identified three main defects on interface subjected to structure level load inputs. The first defect, “fretting,” is a form of micro-slip at the interface caused by reciprocating tangential loading. “Fretting” looks like oxidized, rust-colored points on the interface and is the most visible surface defect. A second defect caused by high impact forces, is plastic damage at the subsurface of the interface, altering the local material behavior. A third effect also caused by high-cycle, reciprocating tangential loading of the interface, is wear debris generated at the contact patch on the interface. How defects affect structural response is an active area of research that requires understanding the complex interactions of material, loading and friction at several length scales. Motivated by observations from structural dynamics, the goal of this research is to quantify how material non-linearity and friction at the contact interface may explain observable defects present at the interface after tribology experiments. Using a computational mechanics frame-work, the FEM (Finite Element Method) is used to develop a model to show how the friction force and local material properties change in response to multi-directional, reciprocating loading on the contact interface. There are four main contributions of this work. The first is the development of an FEM based meso-scale model that captures the contact patch behavior subjected to fretting. The second is the development of the Elastoplastic Friction (EPF) framework to model different friction models and record the energy dissipation generated. This includes the four-parameter Bouc-Wen friction model which, prior to this study had not been used to modeling hysteric behavior of the contact interface. Its use allows the ability to model microslip within an FEM framework. In a third contribution, it was found that with wear, the contact stiffness at the contact interface corresponded to the structures’ stiffness response. And finally, the recognition that in structural dynamics, it is importance to match the structures’ interface slip range to a fretting rig with the same range of micro-slip, otherwise inaccurate structural response may ensue. The results of this study can provide insights about how to design interfaces and assemble structures to limit micro-slip. It also informs on existing jointed interface constitutive models. If integrated within existing structural dynamics FEM models, it has the potential to reduce overall uncertainty present in joint models of these systems.