Numerical model for optimal design of composite patch repair of cracked aluminum plates under tension

In the present work, a numerical model for the optimization of composite patch repair of aluminum plate containing a central crack is developed. The patch is bonded over a cracked aluminum sheet using a small adhesive layer placed in between. The developed model allows us to predict the patch effect on the behavior of the cracked plate under tensile loading and its consequence on the integrity of the structure. To achieve this goal, a finite element model is developed to determine the evolution of the stress intensity factor at the crack tip. After model validation and parametric study, the optimization of the patch volume is formulated and solved by two zero-order and first-order methods. By considering the design variables as the patch height, width and thickness, in addition to adhesive thickness, large reduction of patch material volume can be achieved by applying the developed model. The sensitivity of optimal patch parameters is investigated under various crack lengths. Several stacking sequences and material properties are also considered to reduce the stress concentration in the vicinity of the crack tip, leading to strong volume reduction.