Predictors of cavitation in glassy polymers under tensile strain: a coarse grained molecular dynamics investigation

TL;DR

This study uses coarse-grained molecular dynamics to identify that cavities in glassy polymers under tensile strain nucleate in regions with low bulk elastic modulus, not density or chain end density.

Contribution

It reveals that low elastic modulus regions predict cavity nucleation, challenging previous assumptions about density and stress correlations.

Findings

Cavities nucleate in elastically weak zones.

Cavity position can be predicted from initial elastic properties.

Nucleation is not correlated with local density or atomic-scale stress.

Abstract

The nucleation of cavities in a homogenous polymer under tensile strain is investigated in a coarse-grained molecular dynamics simulation. In order to establish a causal relation between local microstructure and the onset of cavitation, a detailed analysis of some local properties is presented. In contrast to common assumptions, the nucleation of a cavity is neither correlated to a local loss of density nor, to the stress at the atomic scale and nor to the chain ends density in the undeformed state. Instead, a cavity in glassy polymers nucleates in regions that display a low bulk elastic modulus. This criterion allows one to predict the cavity position before the cavitation occurs. Even if the localization of a cavity is not directly predictable from the initial configuration, the elastically weak zones identified in the initial state emerge as favorite spots for cavity formation.