Buckling and postbuckling of truncated conical shells with varying semi-vertex angle: The use of the single perturbation load approach

The importance of taking into account geometric imperfections for cylindrical and conical thin-walled structures in buckling had been already recognized a long time ago. Nowadays, the designers still use empirically based lower-bound methods such as the NASA SP-8007 guideline to calculate the required knock-down factors (KDFs). New design approaches that allow taking full advantage of using composite materials are required. The single perturbation load approach (SPLA), a new deterministic approach developed by Hühne for cylindrical shells, will be investigated with unstiffened composite conical structures. The SPLA's capability for predicting KDF is compared with the NASA approach. The SPLA was applied to perfect conical shells with different semi-vertex angles, and three different positions of the perturbation load were considered. The study contributes to the European Union (EU) project DESICOS, whose aim is to develop less conservative design guidelines for imperfection sensitive thin-walled composite structures.