Modélisation et conception multi-échelles des matériaux : de la description atomique discrète aux modèles du continu. Application aux propriétés amortissantes des pare-brises

Abstract : This thesis focuses on multiscale approaches to model and design multifunctional composite materials for damping applications. The main objective is to develop a multiscale modeling framework that implements hierarchical models from atomistic level modeling to structural level modeling in order to include material creation in the design of the system as a whole. Since damping applications are of interest in this study, we explore some avenues for the design of high loss materials. So, the mean-field micromechanical model introduced by Lipinski et al. [Philosophical Magazine 86 (10), 1305-1326, 2006] is extended to include frequency dependence through the viscoelastic (VE) correspondence principle. The results indicate that with proper choice of VE material properties, it is possible to have a multiphase VE composite with a high loss modulus (good energy dissipation characteristics) for a wide range of frequencies without substantially degrading the stiffness of the composite (storage modulus). Then the slightly weakened interface micromechanical model of Qu [Mechanics of Materials, 14:269-281, 1993] is also extended to investigate imperfect interface effect on damping behavior of viscoelastic composite materials. In order to investigate the nanosize effect on damping caracteristics of nanocomposite materials, we develop and validate an atomistic-continuum interface model for effective properties of elastic composite materials containing ellipsoidal nano-inhomogeneities. This approach bridges the gap between discrete systems (atomic level interactions) and continuum mechanics. An advantage of this approach is that it is developed from earlier models that consider inhomogeneities shape, thereby enabling both the nano-inhomogeneities shape and the nano-interphase shape to be simultaneously accounted for in computing the overall composite stiffness with any case of material and surface/interface anisotropies. On structural level modeling, we developed an analytical tool to study the static behavior of laminated glass beams with silicone material at ends. Then two sandwich finite elements have been developed to study static and modal behavior of viscoelastic sandwich beams and plates with complex boundaries conditions. Based on automatic differentiation and asymptotic numerical method, we developed the Diamant MATLAB toolbox which is a powerful tool to investigate many nonlinear problems namely complex non linear eigenvalue problem. Using all theses numerical tools, we investigate the effects of the materials microstructures on the modal and acoustic properties of the automotives windshields. To finish, this work shows a simple example to conceive the windshield materials microstructures to fulfill four design requirements of the whole windshield structure in service by solving a multi-objectives
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Yao Koutsawa. Modélisation et conception multi-échelles des matériaux : de la description atomique discrète aux modèles du continu. Application aux propriétés amortissantes des pare-brises. Autre. Université Paul Verlaine - Metz, 2008. Français. ⟨NNT : 2008METZ030S⟩. ⟨tel-01752597⟩

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