Rate dependence of indentation size effects in filled silicone rubber

Indentation experiments at the nanometer and micrometer range reported in the literature have shown that the deformation of polymers is — similarly to metals — size-dependent. In addition its size dependence, the deformation behavior of polymers is also known to be rate-dependent. Here silicone rubber is con-sidered. In order to characterize the relation between size and rate-dependent deformation indentation tests of silicone at indentation depths of between 30 and 300 microns and loading times of between 1 and 1000 seconds are performed. In these experiments the hardness and dissipation increased with decreasing loading time and decreasing indentation depth. These experimental results are analyzed with a recently suggested indentation model which incorporates a Frank energy-related nonlocal deformation work. It is found that the indentation model is in good agreement with the experimental data. Evaluation of the experimental data indicates that the rate effects are mostly related to the nonlocal, size-dependent deformation. 1.