Influence of Stitching on Skin Stringer Debonding in Stiffened Composite Panels

A potential increase of the out-of plane structural efficiency of laminated composites may be obtained by using 3D reinforcements technologies. In this paper, a numerical study is presented focusing on the effects of a single reinforcement seam of stitches (selective stitching) along the edge of a stringer foot, in a stiffened composite panel. A Finite Element Model has been developed in order to simulate the mechanical behaviour of the stiffened composite panels with selective stitching. The numerical model has been preliminary validated by comparison with experimental data on three-point bending tests on a skin-stringer configuration. The numerical results, in terms of load vs applied displacements, have been found in good agreement with the experimental data proving the effectiveness of the introduced numerical model. The numerical results have confirmed the potential beneficial effects of stitching in terms of delay of the crack initiation and growth.