Failure behavior of a notched plate repaired by a hybrid repair technique (Stop hole bonded composite

Abstract

Generally, bonded repairs are only approved if the primary aircraft structure is cracked and the residual strength significantly exceeds the design limit charge before the bonded repair can be applied.. In order to improve the maintenance effect of the stop hole approach for cracks, a solution of using both techniques (stop hole / bonded composite repairs) are proposed and investigated by finite element analysis. This work presents a study on the effectiveness of the hybrid repair technique in notched panels using both stop drilling hole and bonded composite repair techniques. Several parameters are taken into account: the diameter of the size of hole drilling, the width and the thickness of the composite patch and other parameters are modeled with a elastoplastic behavior of the plate using Abaqus software. A limit-load analysis determines a lower bound to the limit charge of a component and provides an alternative way to estimate plastic collapse for the limit loads. In addition, the limit load analysis had helped to provide an evaluation of the behaviors of structures or components for other failures. The plastic limit load (PLL) was evaluated by a convergent load increment in a wellconfigured finite element analysis with a load of a sufficiently small increment for an elastic-perfectly plastic behavior of the structure. The allowable limit stress on the aircraft is calculated by applying design factors to the plastic limit load (PLL) so that the onset of plastic collapse does not occur. The results proved that the hybrid repair provided the largest percentage in terms of maintenance and the smallest values for the notch stress intensity factor (NSIF) and von Mises stress for most of the hybrid configuration compared to the single repair technique.