On the experimental characterization and response modelling of particulate composite: Application to flaky aluminium-epoxy composite

Abstract

The epoxy-based composites are most commonly used now in the automobile and aerospace industries due to their low weight and high strength. The quasi-brittle nature of epoxy resin, which is not desirable in several applications, can be overcome by adding flaky aluminium additive resulting in a particulate composite. A small volume fraction of flaky aluminium influences the mechanics of epoxy resin in a significant manner (increase in tensile strength and strain at failure by 56 % and 200 %, respectively, comparing with neat epoxy) resulting in a ductile-type failure. The nonlinear, rate-independent (at low loading rate), rate-dependent (at higher loading rate), and inelastic (viscous effect) response, coupled with an internal damage, observed in epoxy-based flaky-aluminium composite is not fully understood due to the complex nature of resulting material. Much of the previous literature focused on modelling, either the rate-dependency or damage at low loading rate, but not capturing everything concurrently.The novelty of present work is a broad framework development for experimental characterization and calibration of particulate composite (flaky aluminium additives in the epoxy matrix) performing uniaxial tension, cyclic loading–unloading, and creep experiments at different displacement loading rates, and subsequent modelling of the constitutive response in a thermodynamically consistent manner. The macro-scale properties of the newly proposed particulate composite are estimated by mean-field homogenization and compared with the corresponding experimental values. The elasto-plastic-damage and visco-plastic-damage material constants are successfully obtained by a novel optimization approach coupling Levenberg–Marquardt algorithm with stress update algorithms. The practical applicability of the obtained material constants is finally demonstrated solving several boundary value problems employing Lemaitre’s ductile damage model.