Modeling the non-isothermal viscoelastic response of glassy polymers

Experimental data are reported on polycarbonate in tensile tests with a constant strain rate and relaxation tests in a wide range of temperatures. It is demonstrated that the growth of temperature results in a decrease in Young's modulus and a strong increase in the relaxation rate. Constitutive equations are developed for the non-isothermal linear viscoelastic response of glassy polymers when the rates of heating/cooling and stress relaxation are comparable. A good agreement is demonstrated between the observations in relaxation tests on polycarbonate, poly(methyl methacrylate), polystyrene, and epoxy resin, and results of simulation. The model is applied to the numerical analysis of creep flow under non-isothermal multi-step thermal programs.