Shape-topology-layout optimization of stiffened shell structures via the Feature-Driven Optimization (FDO) method

In this work, an integrated shape-topology-layout optimization method is developed for stiffened shell structures to match the designs of the skin, openings and stiffeners. The proposed method takes full advantage of IsoGeometric Analysis (IGA), Finite Cell Method (FCM) and Feature-Driven Optimization (FDO). Specifically, the IGA enables accurate structural analysis and facilitates shape optimization of the skin by directly adjusting the control points of Non-Uniform Rational B-Splines (NURBS) skin surface. The FCM enables the use of the fixed structured mesh during the optimization process. The FDO adaptively inserts openings and stiffener features over the NURBS parametric domain for the optimization of skin topology and stiffener layout as easily as for 2D structures. Both implicit and parametric descriptions are jointly used to model openings and stiffener features. The implicit form concerns the level set function (LSF) in favor of the description of topological changes of the skin and the rapid identification of intersections of stiffeners. The parametric form concerns the use of a small number of design variables to produce optimized results with clear and smooth boundaries. Meanwhile, rigidity contributions of stiffeners are merged into the skin surface without the need of mesh conforming between the stiffeners and the skin surface. Representative examples are presented to demonstrate the effectiveness and advantages of the proposed design approach.