Influence of Loading Conditions on Impact Induced Delaminations in Stiffened Composite Panels

In this paper the onset of impact induced delaminations in stiffened composite panels is analysed. The adopted approach is based on the determination of the threshold critical impact force for the impact induced delamination onset. This approach, already used to calculate the damage resistance of composite panels for optimisation purposes by means of linear FEM analyses, is applied to a geometrically non-linear Finite Element Analysis in order to investigate the influence of the loading conditions on the impact damage resistance of the composite panels. An application to a stiffened composite panel is presented in order to underline the sensitivity of the impact damage resistance to the level of load and to the impact location. Finally, indications on a novel approach able to take into account the non-linearities of the structural response of composite stiffened panels to a low velocity impact are given