Damage tolerance of composite runout panels under tensile loading

Stiffener runout regions are of vital importance for the integrity of modern aerostructures due to the abrupt change of the load path. This investigation deals with the structural analysis in terms of damage tolerance of different runout conceptions from experimental and numerical points of view. The specimens are subjected to tensile loading up to structural failure. The experiments revealed that, for each of the configurations here considered, damage is initiated around the runout region at the skin-stringer joint, with a strong dependency upon the specific design, and progresses along the longitudinal path of the joint. Numerically, these panels are analyzed by means of global-local methodologies incorporating interlaminar failure modeling capabilities at local level. For this purpose two numerical strategies based on interface elements formulations are employed: (1) standard Cohesive Zone Models, and (2) the new enhanced three-dimensional version of the Linear Elastic Brittle Interface Model. Computational damage predictions are compared with experimental data, showing the applicability for complex structures of the analysis tools here presented.