Issue 50

F. Larbi Chaht et alii, Frattura ed Integrità Strutturale, 50 (2019) 331-341; DOI: 10.3221/IGF-ESIS.50.28 333 3. Tensile matrix failure for σ 22 + σ 33 > 0   13 2 2 2 2 12 22 33 23 22 33 2 2 2 23 12 1 failure 1 no failure T Y S S                  (3) 4. Compressive matrix failure for σ 22 + σ 33 < 0   13 2 2 2 2 2 12 22 33 22 33 23 22 33 2 2 2 23 23 23 12 1 failure 1 1 no failure 2 4 C C Y S Y S S S                                           (4) 5. Interlaminar tensile failure for σ 33 > 0 2 33 1 failure 1 no failure T Z             (5) 6. Interlaminar compression failure for σ 33 < 0 2 33 1 failure 1 no failure C Z             (6) The numerical prediction presents reliable simulations not only in the sense of the geometry of the numerical model which has been realized by a unique structure in shell elements but also with the criterion of damage related to this region. In other words, no interface between the folds or between the fibers and the matrix. Add to this that our search result was in the overall response of the structure under loading and its failure load. So the numerical computation parameters were in agreement with the convergence of computation, which allows us moreover to go to the evaluation of several geometrical parameters hardly supported by numerical computations. The parameters introduced in the ABAQUS calculation code are: ** MATERIALS *Material, name=Material-1 *Damage Initiation, criterion=HASHIN 2050.,1200., 62., 190., 81., 81. *Damage Evolution, type=ENERGY 45., 45., 0.6, 0.6 *Damage Stabilization 0.003,0.003,0.003,0.003 *Elastic, type=ENGINEERING CONSTANTS 170000.,9000.,9000., 0.34, 0.34, 0.34,4800.,4800.4500., D ESCRIPTION OF MODEL GEOMETRY AND MATERIAL PROPERTIES he geometric finite element model is shown in Figure 1. Material and strength properties for the composite patch material (carbon / epoxy) are shown in Tables 1, 2 and 3 respectively. The laminated carbon / epoxy composite sheet having the following dimensions: Height H = 140 mm, width w = 50 mm, thickness e = 2 mm. A single circular shape with only one dimension of the notch is taken for each stacking sequence. These plates are subjected to an imposed displacement, equal to 2 mm. The modification is positioned around the notch to reinforce and reduce the tension of the damaged area in the course of loading (figure 1). The dimensions of the thicknesses of this modification are according to the volume fraction of fiber and which are as follows: 0.25 mm for a fraction of 50%, 0.2 mm for a fraction of 70% and 0.125 mm for a fraction of 90%. In the tensile behavior, the fixing and loading conditions consist in fixing the structure at one edge in the vertical and longitudinal direction and a traction displacement on the opposite edge, the same thing in the torsional behavior except that the loading is in rotation around the center of the plate. In the case where both types of loading are applied, traction and rotation must be in the same direction. T