# Nonlinear Response of a Polycarbonate in Post-Yield Cyclic Tests

## TL;DR

The paper studies how polycarbonate behaves under different types of stress, revealing nonlinear and complex responses important for modeling similar materials.

## Contribution

The study reveals new insights into the nonlinear and plastic behavior of polycarbonate under cyclic loading, including unexpected volumetric strains.

## Key findings

- Tensile tests showed nonlinear elasticity, ratcheting, and plasticity with increased volumetric strain.
- Compression tests revealed positive plastic axial and volumetric strains unexpectedly.
- Torsional tests showed nonlinear elastic behavior with plastic volumetric strains induced by deviatoric stress.

## Abstract

This paper aims to investigate the mechanical behavior of a polycarbonate through cyclic tensile, compression, and torsiontests atstrain rates that reduce viscous effects for this material. Measurements included axial and transverse strains for uniaxial tests and shear strains for torsion. Tensile tests exhibited nonlinear elasticity, ratcheting, and plasticity, accompanied by an increase in volumetric strain. Compression tests revealed nonlinear elasticity, with the surprising result of positive plastic axial and volumetric strains, accompanied by marginal transverse strains. Torsional tests showed an elastic but nonlinear relationship between shear stress and strain. In these latter tests, positive plastic volumetric strains were observed, which suggests that deviatoric stress can also induce volumetric plastic strains. These findings are of great importance for developing mathematical models of glassy amorphous polymers, and the observations contribute to understanding the complex behavior of such materials.