Cyclic Indentation Behavior of Layered Nanocomposites: Viscoplastic Numerical Study

The indentation behavior of layered metal/ceramic nanocomposites was studied. The primary objective was to examine the evolving plastic deformation in the ductile metal constrained by the hard ceramic layers, during indentation cycling with respect to fixed maximum and minimum indentation loads. The model consists of alternating aluminum and silicon carbide thin films on a silicon substrate, with the Al/SiC layered structure being indented by a diamond indenter. The rate-dependent viscoplastic response of Al was specifically taken into account in the numerical model. Plastic deformation in the ductile Al layers continued to occur during the unloading phase of the first cycle, in addition to during subsequent reload/unload processes. Cyclic plasticity resulted in an open load-displacement loop and the indenter continued to move deeper in accordance with each cycle. For the control model of a thick homogeneous Al layer, there was no hysteresis loop and the transient behavior approached stabilization...