A viscoelastic-viscoplastic constitutive model for glassy polymers

A constitutive model is presented which combines nonlinear viscoelasticity and viscoplasticity into a unified set of equations suitable for multi-axial isotropic deformation. The model includes the effects of hydrostatic pressure, strain rate, and strain hardening which have been observed for thermoplastics in the glassy regime. The constitutive model is implemented into a finite element analysis program and appropriate parameters are identified for a polycarbonate, Capabilities of the model are demonstrated through the evaluation of a hard-body impact problem. (C) 2001 Elsevier Science Ltd. All rights reserved.