Propagations des singularités au travers des arêtes dans les coques minces

On se place dans le cadre de la théorie linéaire des coques minces de Koïter. La coque a une épaisseur relative e est très petite. Elle présente un pli le long d'une courbe qualifiée d'arête.Les différentes simulations numériques illustrent le phénomène de réfraction numérique des singularités traversant une arête formée par deux coques adjacentes dont les surfaces moyennes sont de nature parabolique et/ou hyperbolique . Il apparaît alors que lorsqu'une singularité traverse l'arête celle-ci se propage sur la ou les caractéristique(s) de la coque adjacente sans perte de régularité

Measure of combined effects of morphological parameters of inclusions within composite materials via stochastic homogenization to determine effective mechanical properties

In our previous papers we have described efficient and reliable methods of generation of representative volume elements (RVE) perfectly suitable for analysis of composite materials via stochastic homogenization. In this paper we profit from these methods to analyze the influence of the morphology on the effective mechanical properties of the samples. More precisely, we study the dependence of main mechanical characteristics of a composite medium on various parameters of the mixture of inclusions composed of spheres and cylinders. On top of that we introduce various imperfections to inclusions and observe the evolution of effective properties related to that. The main computational approach used throughout the work is the FFT-based homogenization technique, validated however by comparison with the direct finite elements method. We give details on the features of the method and the validation campaign as well. Keywords: Composite materials, Cylindrical and spherical reinforcements, Mechanical properties, Stochastic homogenization.Comment: 23 pages, updated figures, version accepted to Composite Structures 201

The refraction phenomenon of singularities in thin elastic shells with developable mid-surface in presence of rigid folds: Case of parabolic shells

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Simulation numérique des propagations des singularités au travers des arêtes dans les coques minces cas hyperbolique et parabolique

National audienceSee http://hal.archives-ouvertes.fr/docs/00/59/29/48/ANNEX/r_0ORB1SQ6.pd

EVALUATION OF INFLUENCES OF INTERFACE BETWEEN MATRIX AND INCLUSION BY FFT

International audienceIn order to take into account the effects of interface between matrix and inclusion, an interphase is generated. A numerical homogenization process is considerated, based on multiscale technique to estimate the effective properties of composite structures with the Lippmann-Schwinger equations. The algorithm is based on fast Fourier transform (FFT) which is more convenient and efficient. However, considering an interphase poses problems for FFT. As the interphase is very thin and due to inhomogeneities, the kernel (Green-kernel) must be also modified to get more accuracy in calculation. This approach is especially suitable for high and low contrasts, seeing that the number of pixel representing the same material is limited. This limit reduces the accuracy of FFT. In this framework, the paper studies different approaches to overcome the interphase problem. The effective material properties are estimated by using multilayer interphase as well as equivalent interphase in the homogenization procedure

An efficient and automated 3D FE approach to evaluate effective elastic properties of overlapping random fibre composites

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On efficient and reliable stochastic generation of RVEs for analysis of composites within the framework of homogenization

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Computation of effective electrical conductivity of composite materials: a novel approach based on analysis of graphs

International audienceIn this work we continue the investigation of different approaches to conception and modeling of composite materials. The global method we focus on, is called 'stochastic homogenization'. In this approach, the classical deterministic homogenization techniques and procedures are used to compute the macroscopic parameters of a composite starting from its microscopic properties. The stochastic part is due to averaging over some series of samples, and the fact that these samples fit into the concept of RVE (Representative Volume Element) in order to reduce the variance effect. In this article, we present a novel method for computation of effective electric properties of composites-it is based on the analysis of the connectivity graph (and the respective adjacency matrix) for each sample of a composite material. We describe how this matrix is constructed in order to take into account complex microscopic geometry. We also explain what we mean by homogenization procedure for electrical conductivity, and how the constructed matrix is related to the problem. The developed method is applied to a test study of the influence of micromorphology of composites materials on their conductivity

RVE GENERATION BASED ON MOLECULAR DYNAMICS - APPLICATIONS

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