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.

Automated summary

This study investigates the vibrational characteristics of joined stiffened conical-cylindrical composite shells using experimental, numerical, and analytical techniques. By superimposing the stiffness contribution of the shells and helical stiffeners, total stiffness coefficients are calculated for the entire structure. The derived governing equations are solved using a power series technique, and natural frequencies and mode shapes are obtained through an eigenvalue problem, with good agreement found between analytical, numerical, and experimental results. Effects of design parameters on modal parameters are thoroughly explored.