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Statistical properties of microcracking in polyurethane foams under tensile test, influence of temperature and density
Authors:S. Deschanel  L. Vanel  G. Vigier  N. Godin  S. Ciliberto
Affiliation:(1) Laboratoire de physique, CNRS UMR 5672, Ecole Normale Supérieure de Lyon, 46 allée d’Italie, 69364 Lyon Cedex 07, France;(2) Groupe d’Etudes de Métallurgie Physique et de Physique des Matériaux, INSA de Lyon, 20 Av. Albert Einstein, 69621 Villeurbanne Cedex, France
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.
Keywords:Acoustic emission  Tension test  Foams  Fracture  Power-law scaling
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