A hyperelastic-thermoviscoplastic constitutive model for semi-crystalline polymers: Application to PEEK under dynamic loading conditions

- A hyperelastic-viscoplastic model for semi-crystalline polymers is developed.
- Model includes thermo-mechanical coupling, temperature and rate dependencies.
- Model implemented in a FE code is applied to study polyether-ether-ketone (PEEK).
- Two dynamic problems were analyzed: low velocity impact test and dynamic necking.
- Mechanical behavior under different thermal and strain rate conditions is analyzed.

In this work, a hyperelastic-thermoviscoplastic constitutive model including thermomechanical coupling is presented to predict the mechanical behavior of semi-crystalline polymers. The constitutive model is based on the original approach developed by Polanco-Loria and coauthors (2010) and it accounts for: material hardening due to strain rate sensitivity, temperature evolution during the deformation process due to heat generation induced by plastic dissipation, thermal softening and thermal expansion of the material. The parameters of the constitutive model have been identified for polyether-ether-ketone (PEEK) from experimental data published by Rae and coauthors (2007). In order to analyze the predictive capacity of the model under dynamic conditions, the constitutive model has been implemented in a FE code within a large deformation framework to study two different problems: low velocity impact test on PEEK thin plates and dynamic necking on PEEK slender bar. These problems involve large and irreversible deformations, high strain rates and temperature increment due to plastic dissipation. The analysis determines the interplay between strain rate and thermal effects in the material behavior. The constitutive model presented herein reproduces adequately the mechanical behavior of PEEK under different thermal and loading conditions, demonstrating the importance of considering the coupling between temperature and strain rate.