Damping Analysis of Composite Cylindrical Tube

Two theoretical ways were used to obtain the modal damping of composite cylindrical tubes in this paper. The Timoshenko beam theory was applied by implementing complex modulus method and the modal strain energy method was used in Love’s first order shell theory. A hammer test was applied to obtain modal frequency and damping results of composite cylindrical tubes. By comparing with finite element method and test results, theoretical models show a good agreement. According to the kinetics equation established, the limitation of beam theory was analyzed. Influences of laminated angle, aspect ratio, thickness diameter ratio, boundary condition and circumferential number on damping of composite cylindrical tube were studied. The results show that the shell theory model can afford an accurate analysis of bend modes while the beam theory model only works when the axial vibration dissipation possesses the advantage. The 1st bend modal loss factor decreases with the increase of aspect ratio and tends to be the same when the aspect ratio is greater than 10. The 1st bend modal loss factor changes a little with the increase of thickness diameter ratio. The 1st bend modal loss factor decreases firstly, then increases and decreases a little with the increase of laminated angle. When the laminated anlge is less than 30° and bigger than 75°, the 1st bend modal loss factor reaches the maximum for clamped-clamped boundary, and it reaches the maximum between 30° and 75° for cantilevered boundary.