Issue 49

B. El-Hadi et alii, Frattura ed Integrità Strutturale, 49 (2019) 547-556; DOI: 10.3221/IGF-ESIS.49.51 549 properties of the 2024-T3 aluminum alloy plate, the glass/epoxy composite patch and the FM-77 adhesive are given in table 2. Material Aluminum panel Patch Adhesive L (mm) 100 40 40 W (mm) 50 35 35 t (mm) 2.29 and 6.35 1.44 0.1 Table 1 : Dimensions of the panel, adhesive layer and patch. Material E1 (GPa) E2, E3 (GPa) ν12, ν13,ν23 G12, G13 (GPa) G23 (GPa) Aluminum (2014-T3) 71.3 - 0.33 - - Glass/epoxy 50 14.5 0.33 2.56 2.24 Adhesive(FM77) 1.89 - 0.33 - - Table 2 : Materials properties. The objective of this work is to analyze the effect of the inclination of the crack front in its plane. For this purpose, the crack line is inclined from the patched side toward the un-patched side by different angles Ө = 0°, 15°, 30°, 45° and 60° respectively (Fig. 2.a). Fig. 2.b shows the different inclinations of the crack front, where the mesh refinment indicates the front of the crack and the immediate adjacent region in the plane of the thickness. Then to compare the stress intensity distribution between two different thickness panels, i.e. thin (2.29mm) and thick (6.35mm). Figure 2 (a) skew crack front. (b) Finite element model showing the crack front configuration N UMERICAL MODELING AND BOUNDARY CONDITIONS he model was solicited by applying a cyclic load to the upper edge in the y-direction with a lower edge embedding. So, the plate is subjected to a maximum stress σ=118 MPa with a load ratio of R = 0.05. The analysis was carried out using Abaqus 6.13 software. A three-dimensional finite element method with automatic meshing was carried out on the structure using 8-nodes brick elements and refinement of the mesh was created in the vicinity of the crack tips as shown in figures 3.c. The composite patches ply orientation is parallel to the loading axis. So, as geometry and loading conditions are symmetrical, only one quarter of the specimens were simulated. Due to its simplicity, Paris law is usually used to predict the fatigue life, which can be expressed as [21]:   m da C K dN   (1) T