Multi-mode modeling of global and local deformation, and failure, in particle filled epoxy systems

A three-dimensional representative volume element is used to analyze the local heterogeneous stress and strain distributions, and the onset to failure, in a standard epoxy system filled with sub-micron sized hard and soft particles. Computations are compared with experiments performed in lubricated compression tests that reveal the intrinsic material's response. The response on the macroscopic level, and that of the matrix on RVE level, is captured by a multi-mode constitutive version of the Eindhoven Glassy Polymer model that describes the non-linear viscoelastic pre-yield, yield and post-yield behavior accurately for all deformation rates used. Compared to the single-mode description, the multi-mode variant covers the pre-yield regime correctly and for the hard-particles also the post-yield response. At a local level, multi-modes give increased stress values and more intensified critical events, which is particularly important for quantitatively predicting the onset of failure. This is successfully done by detailed RVE analyses.