Issue 49

N. Kaddouri et alii, Frattura ed Integrità Strutturale, 49 (2019) 331-340; DOI: 10.3221/IGF-ESIS49.33 337 form of stairs since the mechanical properties of the different layers differ from a layer by report to the other depending on the direction of the fiber. 0,0 0,4 0,8 1,2 1,6 2,0 0 2 4 6 8 10 12 Peel stress (MPa) Patch thickness(mm) Crack lenght a= 5 mm Crack lenght a= 20 mm Crack lenght a= 50 mm 0,0 0,5 1,0 1,5 2,0 0 2 4 6 8 10 12 Peel stress (MPa) Patch thickness(mm) Crack lenght a= 5 mm Crack lenght a= 20 mm Crack lenght a= 50 mm 0,0 0,5 1,0 1,5 2,0 0 2 4 6 8 10 12 14 16 Peel stress (MPa) Patch thickness (mm) Crack lenght a= 5 mm Crack lenght a= 20 mm Crack lenght a= 50 mm [0 2 /45 2 /-45 2 /90 2 ] s [0 2 /75 2 /-75 2 /90 2 ] Figure 8 : Variation of the Peel Stress σ 33 as a function of the thickness of the patch for different length of crack . The value of the J-Integral increases considerably if the crack length increases. If the defect is far from the crack and the free edge, the value of the J-Integral will be minimal, because, in these places, the presence of the defect will have no effect on the behavior of the adhesive. If the defect is at the level of the free edges of the adhesive, the value of the J-Integral will be affected since at these places the concentration of the stresses will be important. The defects that are at the core of the adhesive will have a consequence on the value of the J-Integral since they will be close to the crack. These curves show the variation of the J-Integral as well as the constraints in the patch and the adhesive in function of the position of the defect. We can see clearly the positions, which induce maximum values of J-Integral, and stresses in the patch and the adhesive. The maximum values are for the case or the defect is located at the level of the free edge and a close to the crack. [0 8 ] S