Modeling the large-strain constitutive behavior of polycarbonate under isothermal and anisothermal conditions

The tensile behavior of polycarbonate was studied at large strains below the glass-transition temperature. Experiments were carried Out at a series of constant temperatures and also under conditions of falling temperatures. The specimens necked with a natural draw ratio of approximately 2, and the study was mainly focused on the necked material. Isothermal experiments revealed an elastic mechanism that initiated beyond the natural draw ratio. A model consisting of an Eyring process and two Gaussian elastic mechanisms was found to be applicable to both the isothermal and anisothermal stress-relaxation and stressstrain results. The same model also produced reasonable estimates of the stresses generated during the necking process. In addition, a simple relationship between the isothermal and anisothermal stress relaxation was demonstrated. (c) 2005 Wiley Periodicals, Inc.