Issue 49

E. Abdelouahed et alii, Frattura ed Integrità Strutturale, 49 (2019) 698-713; DOI: 10.3221/IGF-ESIS.49.63 707 In order to better compare and group all the effects and their interdependence on the critical bending moment of each situation, this Fig. (12) has been recapitulated under the condition of the same levels of internal pressure and applied temperature. The composite structure does not allow large deformations (ovalization), hence the weak effect of the internal pressure in certain situations. By purely geometrical effect of the elbows and their ovalization in their cross section, the fibers of the composite are subjected locally to the tensions and others to the compressions. The damage to the elbow is more conditioned by the angle than by the bending mode, hence the critical moments observed in the structure with a 30° elbow. Add to this the effect of location of the defect that approaches critical areas of the elbow (tension or compression). Figure 12 : Recapitulative of damage in a) out-of-plane bending moment, b) opening moment, c) closing moment with effect of angular elbows composite structure and default position under thermo-mechanical loaded condition. Effect of the emplacement and default type with different angular elbows and loading conditions on the failure of structure In this part of this study, our work focuses on the response to the damage of various structures by effect of location and quality of defect under the presence of temperature and internal pressure. The presence of defect in itself has a significant effect according to the conditions of our structures in which they are subjected. According to the composite used in its architecture presented by these break parameters that allow several modes of failure, the defect took throughout this study a single form with a single dimension (a / b) = (6/3). The defect zone was presented by a low resistance to damage, which has the effect of destabilizing the structure differently in three selected locations; that in extrados of the elbow in the middle (type 1) near the end (type 2) and at its end (type3). The quality of the defect is illustrated in the Fig. (5) which is presented only according to the thickness by: the defect is following the whole thickness, the half outside or inside and with the end of both sides. The causes of damage in the presence of a defect in the composites of our structure subjected to both the internal pressure and the bending moment are manifold. The effect of defect quality is important under torsion caused by out-of-plane bending moment. The thickness of the elbow is heavily stressed in tension and compression, hence the effect of defect