Issue 46

S. Mokadem et alii, Frattura ed Integrità Strutturale, 46 (2018) 113-123; DOI: 10.3221/IGF-ESIS.46.12 114 reinforcements (silicon carbide, carbon, alumina, boron), but few of them have studied their volume fraction in the material, their morphology and the fiber / matrix interfaces. Recently, some studies have taken into account the effect of corrosion on composite patch repair. Berrahou and Bachir Bouiadjra [7] analysed the damage of the adhesive for different forms of patch in the repair of aluminum plates by composites, The obtained results show that the adhesive damage localized at the level of corrosion and in the sides of the patch, and the rectangular patch offers high safety it reduces considerably the risk of the adhesive failure. In another study, Berrahou et al [8] studied the effect of the corrosion of plate with double cracks in bonds composite repair the obtained results show that the crack on the left side creates a very extensive area of the damaged zone and gives values of the stress intensity factor (SIF) higher than that on the right side. We can conclude that the left crack is more harmful (dangerous) than that on the right side. The protection of aluminum alloys against marine corrosion is a topic that has been widely studied to date. The books dedicated to this subject are numerous and exhaustive [9]. The usual techniques used to protect aluminum have been tested on composite materials (C / Al). About the effect of the patch form, Bachir Bouiadjra et al [10] compared the two rectangular and trapezoidal patch forms. They showed that the trapezoidal shape improves the efficiency and durability of repair. The finite element method has been used for the study of the crack patching by many authors, we can quote: Many researchers have studied crack reinforcement of stiffeners or pre-stresses on the stress intensity factor at the cracks tip or notches by the optical method of caustics [11-13]. The damaged area criterion has been proposed to analyse the damage in the adhesive [14, 15]. This criterion assumes that the material breaks once the measured stress exceeds the ultimate strength of the material. Damage in the adhesive layer occurs when the deformations or stresses in the adhesive are locally larger than the ultimate properties of the materials. The break in the adhesive does not occur by the propagation of cracks in the substrate, but rather by the initiation and propagation of the damaged area in the layer containing defects such as micro-cracks or voids [16]. The surface area of the adhesive is defined by a surface, where the deformations of the maximum permissible deformation and the breaking load of the glue joints have been determined experimentally. This model has been widely used in the literature to predict the detachment of the adhesive. Chang-Su Ban et al [17] introduced modifications on the model of the damage zone of Sheppard et al [15]. The ratio of the damaged area has been suggested for the prediction of the breaking load of the glue joint. For the epoxy adhesive (FM 73), it has been shown that the ratio of the damaged area corresponding to the failure of this adhesive is 0.247. Apalak et al [18] used the damaged zone theory to analysis of the effects of thermal stresses in the glue joint. They showed that damage can be expected in composites as well as in the adhesive when using soaked adhesives. Recently, several papers describing the damage zone theory published. We note the work of [7, 8] which work on the effect of the corrosion on the damage of the adhesive (FM73) on the repair efficiency and we noted also that [19] has estimated the adhesive damage and failure in the bonds composite repair of aircraft structures using modified damage zone theory. Benyahia et al. and Ramji et al. [20, 21] analysed four different shapes (rectangular, trapezoidal, circular and elliptical). Benyahia and Fari Bouanani [22] evaluated the effect of water absorption on the adhesive damage in the bonds composite repair of aircraft structures. In this study, a three-dimensional finite element method is used to analyse the effect of the corrosion on the damage of the FM73 epoxy adhesive of bonded composite repair of aircraft structures. After variation of the crack inclination θ = (15-30-45-60-75)°, and determination of different graphs of the ratio of the damaged zone and the curves of variation of stress intensity factor, one proceeds to the comparison between the different forms of the patch to determine the effect of the angle of the crack. G EOMETRICAL AND FE MODELS or the study of the repaired mode II crack behaviour, we consider an aluminum plate (Al 2024-T3) having the following dimensions: H pl =254mm, W pl =254mm and e pl =5mm, with a crack inclined at an angle θ . The plate is subjected to uniaxial load σ = 100MPa presented in Fig. 1. The crack is repaired with a patch boron / epoxy, the thickness e pa = 1.5 mm and the adhesive (FM-73) properties G pa = 0.420GPa and the thickness of adhesive it’s e ad = 0.15mm. The mechanical properties of the patch plate and of the adhesive are shown in Tab. 1. The geometric shape of the corrosion used is randomly in 3D with a thickness 0.25mm, before repairing the structure, the corroded area is cleaned to remove the Corrosion film and keep the same mechanical properties. F