Dynamic stability of grid stiffened composite cylindrical shells under harmonic exciting axial force

Lightweight aerospace composite structures used in some components like engine thrust, can experience oscillations which may result in effects like dynamic instability which may be destructive due to excitation of the bending mode vibrations in lateral directions. In this paper, parametric instability of the composite grid stiffened cylindrical shells with simply supported boundary conditions under harmonic axial force is investigated. Donnell shell theory is applied for derivation of the governing equations of the dynamic stability problem. Equivalent stiffness of the shell is calculated using smeared stiffness method. Simplifying the governing equations leads to a system of Mathieu-Hill equations which are solved using Bolotin’s method. The bifurcation frequencies and their corresponding instability regions are obtained. Accuracy of results is confirmed by making comparison with those reported in the literature. The present results show that increasing the angle of helical rib stiffeners, the bifurcation frequency is increased and the corresponding instability region is decreased