Imperfection-Insensitive Axially Loaded Thin Cylindrical Shells

The high efficiency of circular monocoque cylindrical shells in carrying axial loads is impaired by their extreme sensitivity to imperfections and there is an extensive body of literature that addresses this behavior. Instead of following this classical path, focused on circular cross-sections, this paper presents a novel approach that adopts optimal symmetry-breaking wavy cross-sections (wavy shells). The avoidance of imperfection sensitivity is achieved by searching with an evolutionary algorithm for smooth cross-sectional shapes that maximize the minimum among the buckling loads of geometrically perfect and imperfect wavy shells. It is found that shells designed through this approach can achieve higher critical stresses and knockdown factors than any previously known monocoque cylindrical shells. It is also found that these shells have superior mass efficiency to almost all previously reported stiffened shells.