Hadi Salimi - Department of Mechanical Engineering, Malek Ashtar University of Technology, Tehran, Iran.
Ali Davar - Composite Research Centre, Malek Ashtar University of Technology, Lavizan, Tehran, Iran.
Mohsen Heydari Beni - Department of Mechanical Engineering, Malek Ashtar University of Technology, Tehran, Iran.
Jafar Eskandari Jam - Composite Research Centre, Malek Ashtar University of Technology, Lavizan, Tehran, Iran.
Majid Eskandari Shahraki - Department of Aerospace Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.

In this paper, free vibration of laminated composite cylindrical shells reinforced with circumferential rings, are investigated with experimental, analytical and finite element methods and natural frequencies are obtained. The analysis is carried out for clamp-free and clamp-clamp boundary conditions and the results are compared with each other. To solve the problem, the equilibrium Equations of motions are written according to the classical shells theory and after simplification, the structural stiffness and mass matrices and the frequency Equation are derived using Galerkin method. The results obtained in this paper, are compared with the results available in the literatures, and the results of experimental and finite element methods and good agreement is observed.

Boundary conditions, composite cylindrical shells, Free vibration, Galerkin Method, reinforcement rings