Numerical Implementation of a Hyperelastic-Viscoplastic Constitutive Model to Simulate the Mechanical Behaviour of Two Segmented Thermoplastic Elastomer Polymers

Document Type : Original Article

Authors

1 Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran

2 Department of Mechanical Engineering, Isfahan University of Technology, Isfahan , Iran

3 Department of Mechanical Engineering, Isfahan university of Technology, Isfahan, Iran

Abstract

Thermoplastic polyurethane (TPU) elastomers are widely used in industries such as automotive and medical due to their unique mechanical properties. However, their complex deformation behavior, resulting from the interaction between soft amorphous and hard crystalline phases, necessitates accurate numerical modeling for reliable prediction under various loading conditions. This study aims to characterize the deformation behavior of TPU through experimental testing and the implementation of a suitable constitutive model. A phenomenological material framework was developed and implemented in the ABAQUS/Explicit finite element software via a user-defined VUMAT subroutine. The model consists of an equilibrium hyperelastic component representing the soft phase, based on the Arruda-Boyce eight-chain model, and a elastic-viscoplastic- component for the hard phase. The latter is formulated using a linear elastic spring, a nonlinear viscous damper based on a modified Ree-Eyring model, and a frictional element. The model parameters were calibrated using a series of uniaxial compression tests under monotonic and cyclic loading at various strain rates at room temperature. The results showed that, as the fraction of the hard component increased, TPU exhibits stronger plastic behavior, with more energy dissipation and less shape recovery. Moreover, when subjected to a strain of -1.0 after each loading-unloading cycle, it exhibits a residual strain that is not fully recovered even several weeks after the end of the test. Furthermore, the model demonstrates the capability to simulate TPU response under other loading scenarios such as tension and stress relaxation. This work offers physical insight into the deformation mechanisms of TPU and provides a practical modeling tool for its complex elastomeric-plastic behavior.

Keywords

Main Subjects

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