Discrete Stiffness Tailoring: Optimised design and testing of minimum mass stiffened panels

Discrete Stiffness Tailoring (DST) is a novel manufacturing concept where stiffness tailoring is achieved using discrete changes in ply angle to favourably redistribute stresses. Resulting performance increases can be exploited to potentially achieve lightweight rapidly manufacturable structures, uninhibited by the minimum tow-turning radii which limit continuous fibre steering approaches. An efficient two-stage optimisation routine is implemented to design a DST minimum-mass stiffened aircraft wing panel subject to buckling and manufacturing feasibility constraints. The panel is manufactured and compression tested to failure, extending the DST design concept to component level for the first time. A weight reduction of 14.4% is achieved compared to a constant stiffness optimum, through redistribution of load to the stiffener region. The optimum design removes material from the skin, between stiffeners. Experimentally, the optimised tailored panel achieved a buckling load, without failure, within 5% of that predicted, validating both the methodology and modelling.