Free vibrations of a laminated composite coaxial circular cylindrical shell partially filled with liquid

Free vibration of coaxial cylindrical shell made of the angle ply laminated of CFRP partially filled with liquid is analyzed by means of finite element method (FEM) using isoparametric elements. Liquid is assumed to be incompressible and inviscid. The theory is constituted for a coaxial cylindrical shell consisting of multiple wails, and is applied to the numerical calculation in the case of double walls. Bulging in the shell is simulated by FEM in the range of circumferential wave number n ≥ 1, and boundary condition on the free liquid surface is taken into consideration. The ply-angle of the laminated composite, the stored liquid level between outer and inner shells, and the circumferential wave number are chosen as parameters to investigate their effects on the natural frequency and the mode of vibration in the shell. The maximum value appears in the frequency vs. ply-angle diagram for any mode of vibration. It is also shown that hydrodynamic pressure from the stored liquid significantly affects frequencies and modes of the system.