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Etude du comportement mécanique de patchs composites utilisés pour le renforcement de structures métalliques aéronautiques

Abstract : Bonded composite patches are used as structural repairs in several fields of ap-
plication such as civil engineering for damaged concrete structures or aeronautics for
components which exhibit damages, defects or impacts. A similar case of application
consists in using patches for the prevention of defect propagation. The present work
deals with the reinforcement of metallic structures using composite patches in order
to delay the damage appearance.
The proper design requires therefore the use of specific tools to define optimal
characteristics of patches in terms of geometry, number of plies, ply orientations,
location on the structure... A patch optimization programme based on genetic algo-
rithms is developed in this work to reach this goal. The algorithm is associated with
the ANSYS finite element package to calculate the objective function of any rein-
forcement configurations. The programme has been used to design several patches
bonded on structures submitted to different loadings (tensile and shear tests) so as
to reduce stress concentration in a given area.
Main failures are owing to stress concentrations in the adhesive due to the load
transfer from the substrate to the patch. Unidimensional approaches are classically
used in the literature to model the stress distribution in the adhesive, but these
approaches do not account for the difference of the Poisson's ratios between both
the substrate and the composite. Some numerical and analytical models have been
developed from the equilibrium equations obtained along the two directions of the
problem. Bidimensional coupling phenomena are observed, especially at the edges
of the patch when it is rectangular.
At the same time, uniaxial tensile tests have been performed on aluminium spe-
cimens reinforced by rectangular carbon/epoxy patches. The grid method has been
used to measure the displacement field on the patches. Experimental evidence of the
load transfer along the two dimensions of the problem has been obtained. Measure-
ments have been compared with the numerical and analytical models, thus pointing
out some differences due to the assumptions under which models are built.
Document type :
Theses
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https://tel.archives-ouvertes.fr/tel-00159157
Contributor : Jean-Denis Mathias <>
Submitted on : Monday, July 2, 2007 - 2:27:13 PM
Last modification on : Wednesday, October 14, 2020 - 4:10:43 AM
Long-term archiving on: : Thursday, April 8, 2010 - 10:18:03 PM

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  • HAL Id : tel-00159157, version 1

Citation

Jean-Denis Mathias. Etude du comportement mécanique de patchs composites utilisés pour le renforcement de structures métalliques aéronautiques. Matériaux. Université Blaise Pascal - Clermont-Ferrand II, 2005. Français. ⟨tel-00159157⟩

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