Buckling and free vibration study of variable and constant-stiffness cylindrical shells

The ability to steer carbon fibre tapes, varying the tow angle, can widen the designs possibilities of cylindrical shells that are one of the main components of aerospace structures. This research presents experimental and numerical investigation of two carbon fibre reinforced plastic cylindrical shells - a cylinder with conventional layup made of unidirectional prepreg and a variable-stiffness cylinder manufactured by applying fibre placement technology. The shells were tested in compression until buckling and later subjected to a vibration analysis. Load-shortening curves and buckling shapes were acquired during the compression tests, while the natural frequencies and the mode shapes were measured during the vibration tests. Both tests provide a useful data set of the mechanical response of the cylinders which can be applied for further validation of models. The acquired experimental results were compared to a simple, approximated numerical model of the variable-stiffness cylinder showing good correlation with the test results.