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

Abstract

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 shellsa 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.

Teaching buckling of cylindrical shells through an effective laboratory demonstration

“…The shell has a height of 790 mm, an inner diameter of 600 mm and a thickness of 1.45 mm. The shell is made of 8 layers of AS4/8552 carbon fiber reinforced polymer (CFRP).The composite shell was readily available in the laboratory due to a previously conducted research project [19].…”

Measuring geometric imperfections of variable-angle filament-wound cylinders with a simple digital image correlation setup

“…Their method, however, was not able to cover 360 • of the cylinder and an error of 15% between experiments and predictions was found. Labans and Bisagni [27] measured the imperfections of VAT cylinders using a hybrid system, in which the outer surface was scanned using digital image correlation (DIC), and the inner surface with a laser distance sensor. As a key achievement, they found that VAT cylinders are less sensitive to geometric imperfections than constant-stiffness shells.…”

Modelling of fibre steered plates with coupled thickness variation from overlapping continuous tows

“…Since, the benefits of VAT have been used and researched numerically into increasing mechanical properties, such as stiffness [19], buckling [10,18,20,44] and post-buckling [43,42,35] capabilities for laminates alone, or along the interac- tion of stiffeners in a bay design [15,32] and linear buckling of VAT filament-wound cylinders [38]. These benefits have been proven in experiments to increase properties in different applications, such as bending [37] and buckling for cylinders [24,25] and plates [27,29].…”