In this article, free vibration analysis of composite sandwich cylindrical shells with grid cores is investigated experimentally and numerically. In the experimental point of view, the specimens are designed and fabricated using a new silicone rubber mold, and specially designed filament winding setup. After that, the experimental modal test is performed, and natural frequencies are extracted. A 3D finite element model is also built for validation. The comparison of experimental and numerical results showed that there is a good agreement between them. Furthermore, five sandwich shells with different grid cores are investigated, and the best of them are selected. A parametric study is then carried out to investigate the effect of the outer and inner skin thicknesses, rib thickness, ribs’ number, fiber angle of the skin and the boundary condition, on the natural frequency. Finally, sandwich shells are compared with un-stiffened and stiffened shells. Results show that the natural frequency of the sandwich shell is 1.6 and 4.68 times the natural frequency of the stiffened and un-stiffened shells, respectively.
