SIF for cracks repaired with single composite patch having two adhesive bands and double symmetric one in aircraft structures

Finite element method investigation of geometrical influences of adhesive and patch in the safety for 90° elbow piping system

“…To improve the repaired, we must select the new mechanical parameters of the composite patch and adhesive [34][35][36]. The results confirmed that the accuracy of choosing the thickness of the patch lead to improve the repair of the pipeline.…”

“…In the results, we noticed that the increase of elbow thickness leads to decrease the crack rate, which means that a great elbow thickness is recommended to avoid the crack phenomenon especially in the elbow [33]. Figures 8 and 9 show the SIF versus the elbow radius of cracked elbow tip for internal and external zones where the SIF results confirmed that the external position of cracks is more affected than the internal position especially when the values of elbow radius greater than 600 mm [34][35][36]. The percentage nearly of 50% is the reduction ratio of SIF in elbow between two positions, this shows that a high elbows radius at external position allows to transfer the stresses to the critical zone through small period and thus it lead to increase the SIF [34][35].…”

“…The percentage nearly of 50% is the reduction ratio of SIF in elbow between two positions, this shows that a high elbows radius at external position allows to transfer the stresses to the critical zone through small period and thus it lead to increase the SIF [34][35]. After an analysis of results, we can conclude that the repairing by the composite patch is necessary for thin walled elbow [34][35][36]. Finite element method investigation of geometrical influences of adhesive and patch in the safety for 90° elbow piping system 5981 Figure 9.…”

“…The repair by composite patch at crack angle 15° along elbow in the circumferential cracked is investigated by the stress intensity factors (SIF) which are shown in the figure 12. The composite patch with adhesive is played a significant role on the repair technique of cracked elbow, where the SIF is decreased in the cracks external position due to the direct contact between the cracks and the composite patch which absorbed the stress [34][35][36]. For example, the figure 12. is shown the results of the repair by FM73 adhesive type where the SIF values increased to 7.8 MPa.m 1/2 at the maximal pressure during 0.9 mm of adhesive thickness.…”

Implementation of Virtual Crack Closure Technique for Damaged Composite Plates Using Higher-Order Layerwise Model

“…The properly designed patching leads to the asymptotic value of SIF at the crack tip. It means that SIF at the crack tip with patch repair would become independent to crack length [3]. However, the single-side patching may considerably lower the repair efficiency because of out-of-plane bending caused by shift of the neutral plane away from that of a parent plate.…”