A constitutive description of the rate-sensitive response of semi-crystalline polymers

A constitutive model is proposed to describe the quasi-static and high rate large deformation response of semi-crystalline polymers. This model is developed based on an elastic–viscoelastic–viscoplastic framework, to predict the temperature and rate-dependent response of an incompressible semi-crystalline polymer, Nylon 6. Material samples are subjected to high rate compressive and tensile loading using Split Hopkinson Bar devices, and they exhibit a temperature increase, which induces a phase change at the glass-transition temperature. The material parameters in the constitutive model, such as the yield stress, stiffness and viscosity coefficients, are proposed as functions of temperature and strain rate. This study aims to formulate a thermodynamics-based model with minimum parameters, for implementation in FEM software (ABAQUS) by the writing of a user-defined material subroutine (VUMAT). The model is validated via comparison with compressive and tensile experimental test results for material response at different temperatures and deformation rates. It shows good potential in describing the thermo-mechanical response of Nylon 6, and in predicting the dynamic behavior of polymeric material.