Novel cellular perlite-epoxy foams: Effects of particle size

Abstract

The micro-structure and mechanical properties of lightweight porous foams synthesized by dispersing expanded perlite particles (expanded siliceous volcanic glass) in a matrix of epoxy resin were examined. Foams were fabricated with three distinct particle size ranges and, within each size, samples covered a density range of 0.15–0.45 g/cm3. The effects of particle size variation on compressive strength, effective elastic modulus, and modulus of toughness were investigated. An upper and a lower bound were estimated for the elastic modulus of particles in EP/epoxy foams. EP/epoxy foams showed Reuss-like behaviour similar to metals but atypical of non-plastic materials. In addition, results illustrated the significant contribution of the expanded perlite particles in the effective elastic modulus of the foams. Micro-structure of expanded perlite particles was examined and related to their macroscopic properties via two geometrical relationships. Post-test microscopic observations coupled with macroscopic observations taken during the test were used to understand the effect of particle size on the behaviour of the foams under compressive load. Observations revealed the presence of three different failure modes for all foams regardless of their particle size and density; however, the strain to activate each mode was different for each foam type.