FINITE-ELEMENT ANALYSIS OF VIBRATION AND DAMPING OF LAMINATED COMPOSITES

A sandwich composite beam and plate finite superelements with viscoelastic layers for vibration and damping analysis are presented. Each layer is considered as simple Timoshenko's beam or Mindlin-Reissner plate finite element. The energy dissipation in the viscoelastic layers is taken into account with complex modulus of elasticity theory. Two methods for damping analysis of laminated composite beams or plates are considered: the method of complex eigenvalues and the energy method. The first one is an 'exact' method, in which the modal loss factors of structure for each frequency are determined as the ratio of imaginary and real parts of complex eigenvalues. The second method is approximate, in which the modal loss factors of structure for each frequency are calculated as the ratio of dissipated and elastic strain energy for one cycle of steady-state vibrations. For sandwich beams and plates with a viscoelastic middle layer, the vibration and damping analysis for a wide range of materials and geometric parameters was carried out. Comparison of the results obtained by the two methods gives good agreement with the results of other authors.