A Sensitivity Study of the Free Vibration of Composite Sandwich Cylindrical Shells with Grid Cores

In this paper, a sensitivity study of the free vibration of composite sandwich cylindrical shells with grid cores is performed by using Taguchi method. Six parameters such as stiffeners' number, layers' number of inner and outer skins, stiffener thickness, outer and inner skin thicknesses, boundary condition and outer and inner skin ply stacking sequences are considered. To do so, five levels are selected for each parameter. The L25 orthogonal array is selected while longitudinal, circumferential and orthogonal grid cores are considered for the core configuration. A detailed finite element analysis is also used to calculate the natural frequency of composite sandwich cylindrical shells with grid cores. Finally, the effects of the parameters are determined and best levels and optimal conditions were introduced by the analysis of variance and signal to noise analysis. The results show that the boundary condition and skin thickness parameters have a maximum effect on the natural frequency while the stiffener thickness and ply stacking sequence parameters have a minimum effect on it. Also, the effect of layers' number parameter is almost zero. Besides, the natural frequency of composite sandwich cylindrical shells with circumferential grid cores is 368% bigger than unstiffened shells of the same weight. Composite sandwich cylindrical shells with circumferential grid cores are the most efficient structures.