Experimental investigation of repair of impact-damaged aircraft winglet under static bending moments

Bending behaviours of the repaired aircraft winglet were investigated in this paper. Impact damage was firstly inflicted at the center of three pristine winglets by using a drop-weight impact device. The damaged core was restored by filling in the same foam and the damaged skin was repaired by bonding to a three-dimensional scarf patch accompanied with an additional external layer (Doubler). Then, the ultimate load-bearing capacity and failure mechanism of the repaired winglets under static bending moments were studied and compared with the pristine ones. Furthermore, the influence of the stress state of the patch (tension or compression) was discussed by attaching the patch on the top and bottom respectively during testing. The experimental results show that the repaired winglets retain approximately 82% of the load capacity of pristine winglets. Damage occurs along the bolt holes on the composite skin of pristine winglets, while the repaired winglets fail due to the shear crack of the foam and debonding between the foam core and the composite skins. Finally, finite element method were used to explore the failure mechanism for repaired and pristine winglets by comparing the stress distributions. In addition, parametric studies were conducted.