An internal state variable thermodynamic model for determining the Taylor-Quinney coefficient of glassy polymers

In this study, a theoretical model was established for predicting the evolution of the Taylor–Quinney coefficient (β) for glassy polymers, according to the internal state variables thermodynamic framework. The proposed model considers both the strain-softening and the strain-hardening processes simultaneously, making it different from and more complex than previous models. It was found that β depends on both the strain and the strain rate. The Taylor–Quinney coefficient first increases to the maximum value and then decreases with increasing strain, which accords with the experimental results for different strain rates. The evolution of the Taylor–Quinney coefficient was caused by the competition mechanism between the strain-softening part and the strain-hardening part. A simple one-parameter method for predicting the temperature increase at different strain rates was proposed, which fits well with the experimental data and can be applied in practice.