Optimisation of the sizes of bonded composite repair in aircraft structures

In this study the three-dimensional nonlinear finite element method is used to determine the J integral variation along the front of repaired crack with bonded composite patch in aircraft structures. It is known that several parameters influence the repair quality such as the size and the intrinsic properties of the adhesive, the patch and the plate. The experimental design method is used to investigate the effects of patch dimensions (length, width and thickness) in order to achieve an optimisation of the repair operation. This optimisation allows us to determine the most influencing parameters on the repair performances. One can thus help the patch designers to improve the repair quality and durability.

► The width of the patch must be very larger than the crack length.
► Care should be taken while designing patches to avoid higher stresses.
► Patch dimensions have an influence upon the mechanical strength of the assembly.