Utilisation de la technique de corrélation d’images pour l’étude des effets de bord dans les composites stratifiés

Abstract : The use of composite materials has become more and more widespread in many industrial applications. Thanks to Classical Laminates Theory, design of composite structures is today globally well mastered. However, local effects, such as delamination near free edges or junctions, remain a problem. Indeed, mismatches between elastic properties of adjacent plies induce strong three-dimensional interlaminar stresses in the vicinity of free edges and interlaminar interfaces.The aim of this work is to experimentally study these edge effects and to highlight the parameters which could influence them. The approach has consisted in measuring the mechanical fields by Digital Image Correlation at ply scale (mesoscopic scale) on free edges of laminated samples under tensile loading.Three different materials, with different mechanical properties and microstructures have been studied as well as two sample geometries: plane samples and with ply drops. Finite element calculations allowed choosing the stacking sequence [(15/-15)2]s to be studied for experimental tests in which the edge effects are the most important and measurable.The results highlight the presence of displacements gradients and shear strain concentrations near free edges and interlaminar interfaces which depends on the inter-plies gradient of mechanical properties, width of interlaminar interfaces, and presence of a geometrical discontinuity. Moreover, observations at the microscopic scale show the presence of fissures at fiber / matrix interfaces which induce a non-linear shear behavior at mesoscopic scale
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Autre. Ecole Centrale de Lille, 2009. Français. 〈NNT : 2009ECLI0018〉
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Pauline Grosbras. Utilisation de la technique de corrélation d’images pour l’étude des effets de bord dans les composites stratifiés. Autre. Ecole Centrale de Lille, 2009. Français. 〈NNT : 2009ECLI0018〉. 〈tel-00578834〉

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