Vibration behaviours of foam-filled grille composite sandwich cylindrical shells

In this study, a novel lightweight composite sandwich cylindrical shell, namely an all-composite sandwich cylindrical shell (ACSCS) with a hollow grille core (HGC) filled with polyurethane foam (PF), is designed and prepared, and its free and forced vibration behaviours are investigated for the first time. First, an analytical model of the PFHGC-ACSCSs subjected to both base excitation and single-point pulse excitation loads is developed by employing the shear deformation theory enriched by the layerwise method, virtual artificial spring technique, Rayleigh-Ritz approach, modal superposition principle, Newmark-Beta approach, and improved crossfill equivalent theory. Furthermore, the solution procedures for the natural frequencies, mode shapes, and vibration responses in the time and frequency domains of the PFHGC-ACSCSs are defined. Convergence investigations are performed to determine the appropriate truncation numbers and stiffness values for the virtual artificial springs used in the prediction model. Both literature and experimental validations are conducted on the current model, the results of which indicate that it is reliable for predicting the concerned dynamic parameters. Finally, the effects of the critical parameters on the free and forced vibrations of the PFHGC-ACSCSs are studied. The results suggest that the vibration suppression capability could be significantly strengthened by adopting a large core-to-skin thickness ratio, high ratio of the circumferential length of the hollow grille ribs to the whole thickness, large axial and circumferential number of the hollow grille ribs, high ratio of the wall thickness to the circumferential length of the hollow grille ribs, and type of foam with a high elastic modulus. The modelling and solving techniques, preparation processes, testing methods, and conclusions of this study pave the way for the application of such shell structures.