Mechanics of polycarbonate in biaxial impact loading

Abstract

• Biaxial impact of Polycarbonate (PC) plates is investigated numerically and experimentally. • A thermomechanical constitutive model to predict PC dynamic response is proposed. • In biaxial impact, high hydrostatic stresses at low triaxiality levels are developed. • Effective plastic stretch is the invariant that best represents ductile failure. • An extension for criteria modeling ductile/brittle failure competition is proposed. We investigate the deformation and failure behavior of Polycarbonate (PC) under low-velocity biaxial impact loading. For this, we have conducted experiments and numerical simulations of the falling weight impact test (FWT) for different testing configurations. To model PC behavior in dynamic situations, we employed a 3D thermomechanical constitutive model that captures the strain rate, pressure and temperature dependence of deformation response. The finite element model also incorporates adiabatic heating and contact friction effects. Numerical predictions of the FWT force–displacement curves are in good agreement with experimental observations. An assessment of the developed stress–strain fields indicates that the effective plastic stretch λ p is the invariant that most suitably represents the point of material failure in all different test configurations. We examine the relation of a maximum λ p fracture criterion with existing criteria for PC on the grounds of the triaxiality conditions specific to the biaxial impact test. Finally, we propose an extension of these criteria to enhance their capability of predicting failure in part geometries that may become subjected to more complex multiaxial loading scenarios.