On the compressive strength of glass microballoons-based syntactic foams

This work is concerned with particulate composites filled with hollow spherical inclusions, i.e., syntactic foams. We aim at the micromechanical evaluation of the effective uniaxial compressive strength for the most relevant case of glass inclusions of wall thickness of few micrometers (microballoons) filling a thermoset matrix. We develop a three-dimensional Finite Element (FE) modelling which extends and improves that recently proposed by our group. Different microstructures are described by cubic unit cells containing fifty hollow spheres accounting for different filler polydispersions and filler volume fraction f up to 60%. Each microballoon is assumed to undergo brittle failure according to a structural criterion. Here, we account for the matrix nonlinear behaviour and, in a phenomenological way, for the detriment of its mechanical properties, proportional to its defectiveness, which increases with the filler content and becomes extremely relevant at f larger than 50%. Our findings agree with experimental observations from the literature and reveal room for improvement in the effective mechanical properties by acting on the manufacturing process.