Optimisation of stiffeners for maximum fundamental frequency of cross-ply laminated cylindrical panels using social group optimisation and smeared stiffener method

A review of the literature reveals a dearth of research on the maximisation of natural frequencies of laminated composite stiffened panels. The present study combines an analytical solution based on the smeared stiffener method with a novel social group optimisation (SGO) algorithm to develop a procedure for the solution of such an optimisation problem. For this purpose, cross-ply laminated circular-cylindrical panels with a simply supported condition, stiffened by stringers and rings, are considered. The quantities and sizes of the stiffener are optimised to maximise the fundamental frequency of the panels under practical constraints. Example optimisations of various panel geometries are performed. The optimisation results show that the fundamental frequency can be increased significantly by using tailored rings and that for the considered numerical examples, stringers do not make any beneficial contribution to the maximisation of the fundamental frequency. It is also demonstrated that the SGO algorithm is an efficient tool for this kind of mixed-integer constrained optimisation problem.