Patch repair design optimisation for fracture and fatigue improvements of cracked plates

The problem of improving fracture and/or fatigue life of structural components by means of patch repairs is addressed in the present paper by applying a biology-based method, known as the Genetic Algorithm. The optimum design procedure consists in evaluating the patch topology, to be applied to the highest stressed region, which maximises the fracture resistance or the expected fatigue life of the improved structural component by keeping constant the total patched area (constrained optimisation problem). The proposed procedure is implemented in a finite element code and some numerical simulations are carried out in order to assess its reliability. The method is applied to two simple cases of cracked plates under pure Mode I or Mode II: for such analysed configurations, the method allow to improve significantly the fracture or fatigue behaviour of structural components repaired by employing the optimised shape patches instead of a simple shape (e.g. square or rectangular) patches.