Fillet effects on stiffened shell buckling: Experiments & optimization

Stiffened cylindrical shells are widely used in aerospace engineering for their high specific stiffness and strength. However, fillets—inevitable in manufacturing—critically affect key structural properties such as stiffness, weight, and load-carrying capacity, especially in configurations with dense stiffeners. Despite their significant influence, these features have largely been omitted from optimization designs, leading to discrepancies between theoretical predictions and actual performance. In this study, we introduce a novel optimization framework that explicitly incorporates fillet characteristics into the design process. Utilizing a Representative Volume Element method, proposed approach maps fillet features to the design parameter space and quantifies their impact on stiffness. The framework was validated through high-precision buckling experiments and numerical optimization of hierarchical stiffened shells, achieving a load-carrying capacity prediction error of only 0.2 % and a 14 % enhancement in capacity. These results not only underscore the critical role of fillet features but also establish a new paradigm for integrating manufacturing influences into the optimization of thin-walled structures, thereby advancing lightweight aerospace design and manufacturing.