Buckling and postbuckling analysis of shells under quasi-static and dynamic loads

Abstract

Thin-walled fuselage structures, partly subjected to compression and shear (torsion), are endangered by buckling. Present design procedures rest upon nonconservative conditions as to dynamic loading, e.g. landing impact, and on too conservative assumptions, if buckling due to quasi-static loading is considered. With dynamic loading like landing impact a distinction should be made between relatively short and long, quasistatic loading durations, and loadings the durations of which are in the order of the longest lateral period (lowest eigenfrequency) of the structure. A particular problem is to be expected under the later loadings where the interaction of loading dynamics with the dynamics of the buckling process may lead to substantially reduced dynamic buckling loads, as compared with the buckling loads predicted by quasi-static loading. This load reduction actually is not considered in the design process. In order to overcome that problem, a fast and reliable simulation procedure has to be developed. With buckling due to quasi-static loading, experiments have shown that the potential exists for further weight savings with stiffened composite structures by allowing postbuckling of the skin to occur during operation. Proper design enables the structures to act far within the postbuckling regime without any damage. This demand requires the development of an appropriate fast and reliable simulation procedure.