Statistical properties of microcracking in polyurethane foams under tensile test, influence of temperature and density

TL;DR

This study investigates the microcracking behavior of polyurethane foams under tensile stress, revealing power-law distributions in acoustic emissions that vary with temperature and density, and highlighting differences in failure dynamics at low temperatures.

Contribution

It provides new insights into the statistical properties of microcracking in PU foams, especially how temperature and density influence failure processes and acoustic emission patterns.

Findings

Power-law distributions in acoustic energy and waiting times are observed at various densities.

Low temperatures disrupt the power-law behavior in waiting times, indicating more brittle failure.

A plateau in cumulative acoustic energy suggests crack propagation onset.

Abstract

We report tensile failure experiments on polyurethane (PU) foams. Experiments have been performed by imposing a constant strain rate. We work on heterogeneous materials for whom the failure does not occur suddenly and can develop as a multistep process through a succession of microcracks that end at pores. The acoustic energy and the waiting times between acoustic events follow power-law distributions. This remains true while the foam density is varied. However, experiments at low temperatures (PU foams more brittle) have not yielded power-laws for the waiting times. The cumulative acoustic energy has no power law divergence at the proximity of the failure point which is qualitatively in agreement with other experiments done at imposed strain. We notice a plateau in cumulative acoustic energy that seems to occur when a single crack starts to propagate.