Large strain micromechanics of thermoplastic elastomers with random microstructures

TL;DR

This paper introduces new micromechanical models to understand the large strain deformation mechanisms of thermoplastic polyurethanes with disordered microstructures, validated against experimental data.

Contribution

It develops novel models for randomly dispersed and continuous hard domains within TPU microstructures, enhancing understanding of their deformation behavior.

Findings

Models accurately predict large strain behavior.

Dispersed vs. continuous domains influence energy dissipation.

Microstructure geometry affects shape recovery.

Abstract

Thermoplastic polyurethanes (TPU) are block copolymeric materials composed of plastomeric "hard" and elastomeric "soft" domains, by which they exhibit highly resilient yet dissipative large deformation features depending on volume fractions and microstructures of the two distinct domains. Here, we develop a new methodology to address the microscopic deformation mechanisms in TPU materials with highly disordered microstructures. We propose new micromechanical models for randomly dispersed (or occluded) as well as randomly continuous hard domains, each within a continuous soft structure as widely found in representative TPU materials over a wide range of volume fractions, v$_{\mathrm{hard}}$ = 26.9% to 52.2%. The micromechanical modeling results are compared to experimental data on the macroscopic large strain behaviors reported previously (Cho et al. 2017). We explore the role of the dispersed vs. continuous nature of the geometric features of the random microstructures on shape recovery and energy dissipation at the microstructural level in this important class of phase-separated copolymeric materials.