The composite patch bonding technique in the damaged area has demonstrated its effectiveness in reducing stresses at the stress concentration zones and has ensured a long service life of the repaired structure. The search for a suitable adhesive and patch for good load transfer has led researchers to develop, by mechanical tests, analytical or numerical methods, ideas about the shape, nature, stacking sequence type of adhesive for a better combination of patch and adhesive. Our work fits into this context; the aim is to provide a method to reduce the stresses on the plate by protecting the adhesive against the effect of aging, which significantly affects the mechanical properties of the adhesive and the composite patch. Several factors have been highlighted namely, the effect of the composite stacking sequence, modification of the thickness of the plate, the presence of bonding defects in different positions. The analysis of the J-Integral and the stresses in the adhesive and the patch shows clearly that their values depend strongly on these different parameters. However, the modification made to the plate has no effect on the stress concentration.
The repair technique has presented its effectiveness in the reduction of the stresses at the level of stresses concentration areas. The search for a patch and suitable adhesive for a good transfer of load has pushed researchers to develop many ideas, which relate the form, the nature, the stacking sequence of the patch and the adhesive type to give a better combination of choice between the patch and the adhesive. Our work fits in this context; the objective is to analyze by the method of finite elements the behavior in the rupture of a damaged plate in the presence of defect of bonding. The analysis of J-Integral and stresses in the tow substrates adhesive and patch shows clearly that their values depends strongly on the position of the default essentially when it's located close to the free edge of the free edge of the adhesive or the crack.
The presence of a geometric discontinuity such as a crack or a notch can cause the failure of a structure during its use. Under various mechanical or thermal stresses, a high concentration of stresses can take place at the level of these discontinuities, which in most cases will lead to the total failure of the structure. The service life of these structures can be improved with the use of the repair technique by bonding a composite patch. This technique is of significant interest in several fields, especially with the use of composite materials. This technique is widely used in aeronautics and ensures a long life of damaged structures. Current research aims to optimize the shape size and fiber's nature of this composite patch in order to ensure good load transfer by reducing the stresses in the damaged area. In this work, a finite element method is used to analysis the effect of the shape of the patch on the global response of a 2024-T3 aluminum structure in the presence of a central circular notch. The composite patch is of the carbon/epoxy type bonded through an A-140 Adekit type adhesive on the damaged part of the plate. The analysis consists in determining the force-displacement curves of the repaired structure by using the combination of the two techniques, XFEM for the damage of the aluminum plate 2024-T3 by the automatic creation of the crack and CZM for the analysis of the adhesive debonding. The analysis takes into account the damage in the plate and in the adhesive. However, for the composite patch, and since there will be no damage, we have just analyzed the effect of its shape and essentially the shape of its edges on the load transfer and consequently on the resistance of the structure under loading in tension. Two main patch shapes have been highlighted, namely the square and circular shape. The results show clearly that the shape of the patch’s edges has an impact on the stresses reduction in the plate and subsequently ensures good resistance in terms of force-displacement curve and consequently delays the peeling of the adhesive.
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