Numerical-experimental study on the compressive behaviour of repaired composite panels

Barely Visible Impact Damages (BVID) caused by impact phenomena during maintenance and in-service missions can be a critical issue for composite structures. BVIDs may induce delaminations and intra-laminar damages, which can considerably reduce stiffness and strength of composite laminates leading to component replacement or repair. This work is aimed to numerically and experimentally investigate the mechanical behaviour of a repaired aeronautical composite stiffened panel subjected to compressive loading conditions. A numerical activity has been performed by introducing Finite Element models in the ABAQUS FEM environment with the aim to numerically simulate the mechanical behaviour of the investigated stiffened panel configuration. Indeed, a pristine panel configuration and a repaired panel configuration have been numerically modelled. In the repaired configuration a stepped bonded patch has been used to simulate the repair process. Then, an experimental testing activity has been performed on the repaired stiffened panel configuration and experimental data have been compared to results obtained from the numerical studies for model validation purposes. The validated numerical model has been used to perform a sensitivity analysis on the compressive behaviour of repaired stiffened panels with patches to assess the influence of stacking sequence and sizes of the repair patches on the panel's mechanical behaviour. Although other components are involved in the tightness of the repair patch, the work proved that the stacking sequence of the patch play the main role in the effectiveness of the process in recovering the mechanical performances and overall behaviour of the component.