Modeling the Non-linear Viscoelastic Response of High Temperature Polyimides

TL;DR

This paper introduces a thermodynamic-based constitutive model to predict the non-linear viscoelastic behavior of high-temperature polyimide resins, validated against experimental data for specific polyimide types.

Contribution

A novel thermodynamic framework for modeling polyimide viscoelasticity, incorporating natural configuration evolution and entropy production maximization, specific to high-temperature applications.

Findings

Model accurately predicts viscoelastic response of polyimides

Good agreement with experimental data for PMR-15 and HFPE-II-52

Provides a thermodynamic basis for high-temperature polymer modeling

Abstract

A constitutive model is developed to predict the viscoelastic response of polyimide resins that are used in high temperature applications. This model is based on a thermodynamic framework that uses the notion that the `natural configuration' of a body evolves as the body undergoes a process and the evolution is determined by maximizing the rate of entropy production in general and the rate of dissipation within purely mechanical considerations. We constitutively prescribe forms for the specific Helmholtz potential and the rate of dissipation (which is the product of density, temperature and the rate of entropy production), and the model is derived by maximizing the rate of dissipation with the constraint of incompressibility, and the reduced energy dissipation equation is also regarded as a constraint in that it is required to be met in every process that the body undergoes. The efficacy of the model is ascertained by comparing the predictions of the model with the experimental data for PMR-15 and HFPE-II-52 polyimide resins.