Evaluation of Mixed-Mode Center Crack SIF in a Curved Plate Repaired by Stop Holes, Composite Patch, and Hybrid Methods

In this research, using the 3D finite element method and considering different materials for a composite patch, the effect of separate and simultaneous use of stop holes and composite patch (one-sided and two-sided) on reduction of SIF in a curved plate including mixed-mode crack is investigated. Glass-epoxy, graphite-epoxy, carbon-epoxy, and boron-epoxy are used for repair patches.  For the one-sided patch, the effects of different geometric parameters on the efficiency of the repair are investigated. For all four composite patches, as the thickness of the patches increases, KI and KII decrease, but with increasing the patch length, KI and KII increase. The research results also show that with increasing the width of the glass-epoxy patch, KI and KII almost do not change, but for other patches, as the patch width increases, the SIF increases. The effect of the radius of curvature of the plate on the efficiency of various repair methods is also investigated. In all repair methods studied, SIF decreases with increasing radius of curvature of the curved plate. Different repair methods are compared and the best method with the highest efficiency is introduced. The best repair mode is the hybrid repair method (stop-holes and two-sided boron-epoxy patch), which reduces KI and KII by 84.50 and 86.6%, respectively. Finally, the effect of adhesive thickness used for patch bonding on hybrid repair method efficiency and durability is investigated. for all four materials of patches understudy, KI and KII increase with increasing the thickness of the adhesive, but on the other hand, as the thickness of the adhesive increases, the maximum Von Mises stress in the adhesive decreases.