A micromechanical model for quasi-brittle compressive failure of glass-microballoons/thermoset-matrix syntactic foams

We propose a micromechanical model for the quasi-brittle failure of syntactic foams subject to uniaxial compression. We focus on a failure characterised by shear bands inclined of about 45° with respect to the loading axis, often observed in thermoset polymers filled with glass microballoons. Our objective is to develop a three-dimensional Finite Element (FE) model for the effective compressive strength. Towards this aim, we extend our previous FE models, which include fifty randomly placed balloons and were developed to assess the accuracy of linear elastic homogenisation procedures for syntactic foams. Here, we account for the filler polydispersion and introduce a novel structural failure criterion for the glass microballoons. The proposed models are shown to be macroscopically isotropic with respect to the effective strength. We find good agreement with experimental results from the literature on syntactic foams with filler volume fraction of 60%, for which we assume the matrix to be linear elastic.