Mechanical Response of Variable and Constant-Stiffness Cylindrical Shells for Launcher Structures

The ability to steer the carbon fibre tape, varying the tow angle can open new designs of cylindrical shells – the main structural component of the space launcher vehicles. This research presents experimental and numerical investigation of two carbon-epoxy cylindrical shells – a cylinder with conventional layup made of unidirectional prepreg and a variable-stiffness cylinder manufactured by applying advanced fibre placement technology. The shells were tested in compression until buckling, measuring load-shortening and capturing the buckling shape by digital image correlation systems. For the purpose of modelling the variable-stiffness cylinder, a simplified stiffness approximation approach was applied. The obtained load-shortening curves and buckling shapes demonstrated good correlation with non-linear numerical models. The results of the investigation contributes to the understanding the phenomenon of buckling of variable-stiffness cylindrical shells, and the influence of initial geometric imperfections and thickness variations.