Thermomechanical Modeling of Microstructure Evolution Caused by Strain-Induced Crystallization

TL;DR

This paper presents a thermomechanical model for strain-induced crystallization in polymers, capturing microstructure evolution and temperature effects during cyclic tensile tests, with numerical validation using FEM simulations.

Contribution

It introduces a novel thermomechanical modeling approach based on a triple decomposition of deformation and thermodynamic principles for polymers undergoing crystallization.

Findings

Model successfully simulates crystalline region formation and degradation.

Temperature distribution during cyclic loading is accurately predicted.

Numerical examples demonstrate microstructure evolution in different samples.

Abstract

The present contribution deals with the thermomechanical modeling of the strain-induced crystallization in unfilled polymers. This phenomenon significantly influences mechanical and thermal properties of polymers and has to be taken into consideration when planning manufacturing processes as well as applications of the final product. In order to simultaneously capture both kinds of effects, the model proposed starts by introducing a triple decomposition of the deformation gradient and furthermore uses thermodynamic framework for material modeling based on the Coleman--Noll procedure and minimum principle of the dissipation potential, which requires suitable assumptions for the Helmholtz free energy and the dissipation potential. The chosen setup yields evolution equations which are able to simulate the formation and the degradation of crystalline regions accompanied by the temperature change during a cyclic tensile test. The boundary value problem corresponding to the described process includes the balance of linear momentum and balance of energy and serves as a basis for the numerical implementation within an FEM code. The~paper closes with the numerical examples showing the microstructure evolution and temperature distribution for different material samples.