Towards a coupled structural and economical design procedure of unstiffened isotropic shell structures

Thin-walled structures such as those used for space launch vehicles are prone to buckling when axial load is applied. These structures can be designed as imperfection-sensitive structures in the form of unstiffened shell structures or else as imperfection-tolerant structures by applying frames and stringers to the shell structure. Weight-Strength-Curves can be applied to compare structural concepts from a pure technological point of view, where neither costs of manufacturing nor the manufacturing signature are taken into account. Within this paper, a cost model for unstiffened isotropic shell structures based on the assembly out of multiple panels is introduced. Furthermore, a relation between the manufacturing process and the load carrying capacity of an isotropic shell structure is derived. On this basis a coupled structural and economical design procedure is evolved. In a final step, an example is introduced in order to illustrate the application of the coupled design procedure and to derive a structure which is optimized with regard to its structural mass and manufacturing costs. Based on this example it is shown that the chosen panel size affects not only the manufacturing costs, but also the load carrying capacity.