VIBRATION AND NEAR SCATTERING FIELD OF IMMERSED RECTANGULAR ELASTIC-VISCOELASTIC COMPOSITE PLATE IN AN UNDERWATER SOUND FIELD （I）——ANALYSIS OF RECTANGULAR COMPOSITE PLATE SYSTEM

Basing on theory of elasticity, according to least elastic energy and variational method, the position of neutral plane of the elastic composite plate system is determined. And then, the governing equations for the flexural vibration of composite elastic-viscoelastic laminar plates are derived.
It is shown, that the governing equations and boundary conditions of this composite plate system are similar to those of thin plate, if the equivalent rigidity, Poisson's ratio and surface mass density are instead of the parameters in equations and boundary conditions.
The general solution for bending motion of this plates system is given by the method of normal mode analysis and Fourier analysis. As an example, a simply-supported, rectangular composite plate system is concerned. The equivalent rigidity, Poisson's ratio and surface mass density for bilaminar plate systems with steel as base plate coating with rubber, plastic or ceramic layer are numerically calculated. The damping constant, resistant coefficient and natural frequency for different vibration mode of this system with edges simply-supported are calculated also.