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Dynamic fracture in brittle amorphous materials : Dissipation mechanisms and dynamically-induced microcracking in PMMA

Abstract : Crack propagation is the fundamental mechanism responsible for catastrophic breakdown of brittle materials, and is usually described by the Linear Elastic theory of fracture. However, this theoretical framework is only relevant to slow crack propagation and fails dramatically at high velocities. In particular, it accounts neither for the experimentally observed maximal crack velocities, nor for the roughness of the post-mortem fracture surfaces obtained in the high velocity regime. In order to investigate these phenomena, we have designed an experimental setup that allows to study the fracture mechanisms in a model brittle material, namely PMMA, over a wide range of velocities at small space and time scales. This apparatus has enabled us to evidence a new critical velocity beyond which crack propagation is accompanied by macroscopic damage through the nucleation and growth of microcracks ahead of the front. A simple scenario allows to take this damage into account in the so-called fracture energy, i.e. the energy dissipated as the crack propagates over a surface increment, and may succeed to explain the abnormally low limiting crack velocity observed in brittle materials. It explains also the
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Submitted on : Tuesday, July 20, 2010 - 4:39:25 PM
Last modification on : Sunday, February 18, 2018 - 9:26:29 AM
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Claudia Maribel Guerra Amaro. Dynamic fracture in brittle amorphous materials : Dissipation mechanisms and dynamically-induced microcracking in PMMA. Physique [physics]. Ecole Polytechnique X, 2009. Français. ⟨pastel-00006135⟩

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