A master’s thesis by student Zainab Najeh Jassim, University of Basra, College of Engineering, Department of Mechanical Engineering, was discussed under the title: Fracture Mechanics Analysis for Patched Cracks with Different Shapes Using Extended Finite Element Method (XFEM) To extend the operating life of defective structures, a repair procedure based on composite patches was used to reinforce cracked components. Due to the numerous benefits of composite materials, this technology has piqued the interest of academics and engineers. The objective of this study is to investigate the effect of patch presence on the stress intensity factor (SIF) before and after repair with patches made of steel patches and composite patches made of glass fiber-reinforced polymer composite patches (GFRP) and carbon epoxy patches in different shapes: circular, rectangular, and trapezoidal, under two conditions: unsymmetric patch (one patch) and symmetric patch (two patches).Two types of crack specimens were used (edge and central cracks).
The stress intensity factor (SIF) was calculated using the Extended Finite Element (XFEM) method for the steel patch and the traditional FEM method for the composite patch in different shapes, circular, rectangular, and trapezoidal patches, under the specified boundary conditions and loading parameters using the ABAQUS programmer.
The results showed that circular and rectangular steel patches are more effective than trapezoidal steel patches. The symmetric patch arrangement (two patches) is better than the unsymmetric patch arrangement (one patch) because it significantly reduces the stress intensity factor (SIF), In addition, it was demonstrated that the stress intensity factor (SIF) values are unaffected by the various forms of patches (circular, rectangular, and trapezoidal) for both GFRP and carbon-epoxy composite patches. regardless of whether they are used in unsymmetric (one patch) or symmetric (two patches) configurations. Furthermore, it was demonstrated that the orientation of the fibers in the composite patch (GFRP, carbon-epoxy) has a substantial impact on the effectiveness of the patch ,So the sequence of stacked composite laminates in the

uniaxial direction [90] has the most significant impact on the stress intensity factor (SIF), while the stacking composite laminate [0], in comparison, has the smallest impact on the stress intensity factor (SIF). The steel patch performs better than the carbon-epoxy and GFRP composite patches because it lowers the stress intensity factor (SIF) considerably. So it's more efficient than GFRP patches. GFRP composite patches, on the other hand, have the least effect on the stress intensity factor (SIF).