Issue 49

N. Kaddouri et alii, Frattura ed Integrità Strutturale, 49 (2019) 331-340; DOI: 10.3221/IGF-ESIS49.33 334 Materials E 1 (MPa) E 2 (MPa) E 3 (MPa) G 12 (MPa) G 13 (MPa) G 23 (MPa) Carbon /Epoxy 128600 9766 9766 0.346 0.346 0.346 5252 4364 4364 Table 3 : Mechanical properties of the composite patch Carbon/epoxy. In order to see the effect of the fibers orientation in the composite patch on the global behavior of the repaired structure, six stacking sequences were selected as shown in the Tab. 4. Laminates S1 S2 S3 S4 S5 S6 Stacking Sequence [0 8 ] s [0 2 /15 2 /-15 2 /90 2 ] s [0 2 /30 2 /-30 2 /90 2 ] s [0 2 /45 2 /-45 2 /90 2 ] s [0 2 /60 2 /-60 2 /90 2 ] s [0 2 /75 2 /-75 2 /90 2 ] s Table 4 : Different stacking sequences used in the composite. M ESH AND BOUNDARY CONDITION he boundary conditions for the repaired plate in traction are reproduced in the following manner: • Embedding the lower face of the plate u1=u2=u3=UR1=UR2=UR3=0, • Pressure at traction to the other face of the Amplitude P=50 MPa. Figure 3 : Model of the repaired structure under traction. The numerical analysis has been carried out by the ABAQUS code using the finite elements methods. The structure been meshed by elements of hexagonal type linear C3D8R (Fig. 4). A refined mesh is carried out to the side of the crack and at the level of the patch and the adhesive; the adhesive has been considered as a third material so that one can introduce its mechanicals properties. The contact is considered as being perfect between the different layers (adhesive-patch, adhesive- plate and between the different layers of the composite). An elasto-plastic analysis is considered for the plate and the adhesive by introducing the plastic part of the two curves of the tensile test of the plate and the adhesive. For the composite, the mechanical properties has been varied the sequence of stacking (orientation of the fibers) and the Nature of the fibers, for this, one has used the CADEC code designed specially to determine the engineers constants of the composite. R ESULTS AND ANALYSIS he Fig. 5 shows the variation of the J-Integral as a function of the length of the crack; we note clearly that the value of the J-Integral is low compared to the case of the plate unrepaired. It should be noted that the value of the J-Integral increases with the increase in the length of the crack. The slope of the curve becomes more acute and the value of the J-Integral increases. T T