An analysis methodology for failure in postbuckling skin-stiffener interfaces

Blade-stiffened structures have the potential to produce highly efficient structures, particularly when the large strength reserves available after structural buckling, in the postbuckling range, are exploited. In experimental tests of postbuckling stiffened structures made from fibre-reinforced composites, failure typically initiates at the interface of the skin and stiffener and leads to rapid and even explosive failure. A methodology has been developed for analysing collapse in postbuckling composite structures that involves predicting the initiation of interlaminar damage in the skin-stiffener interface. A strength-based criterion is monitored in each ply using a local model of the skin-stiffener interface cross-section. For the analysis of large structures, a global analysis is first run to obtain the complete postbuckling deformation field, which is then input onto a local model using a global-local analysis technique. The coordinates of the local model can easily be moved to rapidly assess failure initiation at numerous skin-stiffener interface locations throughout the global structure. The analysis methodology is compared to experimental results for two-dimensional T-section specimens and large, fuselage-representative stiffened panels and is shown to give accurate predictions of the failure load and failure mechanisms. The use of the approach for the analysis of postbuckling composite structures has application for the design and certification of the next generation of aircraft.