Finite element analysis of damped vibrations of laminated composite plates

Abstract

<p>In this thesis, the damped free vibrations of composites are treated from the viewpoint of macromechanical analysis. Two damping models are developed, namely: the Viscoelastic Damping (VED) model and the Specific Damping Capacity (SDC) model. The important symmetry property of the damping matrix is retained in both models. A Modified Modal Strain Energy method is proposed for the evaluation of modal damping in the VED model using a real, instead of a complex, eigenvalue problem solution. Numerical studies of multi degree-of-freedom systems are conducted to illustrate the better accuracy of the method compared to the Modal Strain Energy method. The experimental data reported in the literature for damped free vibrations, in both polymer-matrix and metal-matrix composites, were used in the finite element analysis to test and compare the damping models. The natural frequencies and modal damping were obtained using both the VED and the SDC models. It was shown that the results from both models are in satisfactory agreement with the experimental data. Both models were found to be reasonably accurate for systems with low damping. Parametric studies were conducted to study the effects on damping of the side-to-thickness ratio, the principal moduli ratio, the total number of layers, the ply-angle and boundary conditions.</p>