On the free vibrations of joined grid-stiffened composite conical-cylindrical shells

The present study aims to investigate the vibrational characteristics of joined stiffened conical-cylindrical composite shells using experimental, numerical and analytical techniques. The stiffness contribution of the shells and helical stiffeners have been superimposed by means of a smeared approach in order to calculate the total stiffness coefficients of the whole structure. The governing equations have been derived according to Donnell’s shallow thin shell theory and then solved using power series technique. Applying boundary conditions along with continuity conditions at the interface section of the shell segments, the natural frequencies and mode shapes of the grid-stiffened joined conical-cylindrical shells are obtained through an eigenvalue problem. The experimental modal analysis has been carried out on the real specimens made of monolithic and wound glass fibers using a specially-designed filament winding device. For further validation, 3-D models have been built in ABAQUS CAE software and analyzed using finite element analysis. In order to verify the present model, several comparisons have been made which indicate a good agreement between the analytical, numerical and experimental results. Furthermore, the effects of several design parameters such as the cone semi-vertex and stiffeners’ orientation angles on the modal parameters have been thoroughly investigated. • The free vibrational behavior of joined grid-stiffened composite conical-cylindrical shells are investigated. • The samples are fabricated from E-glass, woven glass fiber and epoxy resin during filament winding process. • The natural frequencies and corresponding mode shapes are obtained through modal testing and numerical analysis. • The analytical method is abale to predict the vibrational behavior of joined grid-stiffened shells. • The effect of some geometrical properties and various design parameters on the natural frequency are examined.