Coupled vibrations of viscoelastic three-layer composite plates. 2. Numerical experiments

Results of numerical studies of the influence of reinforcement orientation of hard layers and the relative thickness of the soft layer of an isotropic viscoelastic polymer on the values of natural frequencies and coefficients of mechanical losses are discussed. In a symmetrical three-layer plate, a bending-torsion interaction arises, generating mutual transformations of the eigenmodes of the coupled vibration modes, if at least one of its own forms in plate directions is characterized by an even number quarters of a wave, and another proper form - an odd number of quarters the waves. In an unsymmetrical asymmetric three-layer plate, bending-bending interaction arises, generating mutual transformations eigenmodes of coupled vibration modes in two mutually orthogonal planes if in the main directions of the plate both of their own forms characterized by either an even or an odd number of quarters of a wave. It was found that each mode of natural vibrations of three-layer plates corresponds to the effective relative thickness of the soft isotropic layer viscoelastic polymer.