Experimental and Numerical Study of Composite Omega Stringer - Skin debonding under Flexural Loading Conditions

The present work is focused on the study of the damage behaviour of a composite reinforced panel under quasi-static bending loading conditions. The investigated reinforced composite structure, consisting of a curved CFRP panel reinforced and a co-cured CFRP omega stringer, can be considered representative of a regional aircraft fuselage stiffened skin section. The bending loading conditions have been simulated by means of both 3-point and 4-point bending tests. A first numerical sensitivity study has been performed, in order to investigate the influence of boundary conditions (spacing span and size of the rollers, number of loading points, etc) on the flexural driven inter-laminar damage. Then, the damage behaviour of a representative selected test article has been deeply investigated by detailed numerical models able to take into account both the inter-laminar and intra-laminar damages onset and evolution. A first validation has been attempt by comparing the obtained numerical results for this selected specimen, in terms of stiffness and debonding area, with data taken from experimental tests and non-destructive inspections (NDI). Finally, the influence of the FE formulation on the accuracy of the numerical model and on the related computational costs has been assessed by comparing the results obtained with shell layered elements or ply by ply 3D elements formulations in order to attempt the definition of an effective modelling strategy for the investigated composite structural element.