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Etude de la compaction dynamique de mousses polymères : Expériences et modélisation

Abstract : Polymeric foams are widely used in many industrial applications as thermal insulators, structural materials or shock mitigators. Indeed, they are lightweight materials with an excellent weight/stiffness ratio and low production costs. One of the applications which interests the CEA is the protection of structures against mechanical loadings generated by laser irradiations or high velocity impact of small debris. The main objective of this PhD thesis is to investigate the mitigation capability of an expanded polyurethane foam and an epoxy syntactic foam against extremely fast (> 10^6 s^-1) and intense (> 10 GPa) dynamic loadings. Cyclic quasi-static tests and dynamic experiments have been performed to investigate the behavior of these two foams for strain rates ranging from 10^-3 to 10^6 s^-1. Analysis of the experimental results shows that these polymeric foams have an elastic behavior phase followed by a compaction phase with significant permanent sets. Compaction thresholds are about 9 MPa for the polyurethane foam and 30 MPa for the epoxy foam under quasi-static loadings and around 21 MPa for the polyurethane foam and 72 MPa for the epoxy foam for strain rates above 10^4 s^-1. Two porous compaction models are developed to represent the macroscopic behavior of these foams for such strain rates. The parameters are identified from the results of dynamic compression experiments (gas gun, low inductance generator). The validity of the models is tested by comparing calculated velocity profiles with an explicit hydrocode and velocity profiles measured during the experiments. These models are then used to analyze the results obtained with electron beam irradiation and laser-driven shock experiments. We demonstrate that the studied polymeric foams have high mitigation capabilities and that the models are valid for high strain rates.
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Submitted on : Monday, March 19, 2018 - 6:21:34 PM
Last modification on : Thursday, July 26, 2018 - 11:42:01 AM
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Pierre Pradel. Etude de la compaction dynamique de mousses polymères : Expériences et modélisation. Mécanique des matériaux [physics.class-ph]. Ecole Nationale Supérieure de Mécanique et d'Aérotechnique - Poitiers, 2017. Français. ⟨tel-01737770⟩

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