• Deschanel, Stéphanie

Abstract

In order to predict failure time of materials, a new approach has been considered : fracture can be viewed as a critical phenomenon. For some materials fracture can be seen as a clustering of microcracks. We focus on heterogeneous materials (vitreous polymer foams) whose fracture can be described as a phase transition. Our main experimental tool is the monitoring of the acoustic emission signatures of the microfractures, which occur during mechanical tests. We highlighted diffuse microcrack nucleation and progressive localization into a dominating crack with a good fit of the energy by a power law. The exponent of this power law does not seem to depend neither on the material density, the loading mode, nor the behavior law. The time intervals between two damaging events seem to be power law distributed only if the stress remains nearly constant for the most part of the test. A critical region where the cumulative energy could be described by a power law appears only for creep tests.

Topics

• density
• impedance spectroscopy
• polymer
• phase
• crack
• phase transition
• acoustic emission
• creep
• creep test
• clustering