AN ANALYTICAL METHOD FOR WAVE PROPAGATION IN A FLUID-LOADED COMPOSITE LAMINATED PLATE

Abstract

An analytical method is presented for studying elastiodynamic responses of an infinite fluid-loaded composite laminate subjected to a Gaussian beam pressure. In this method, the plate is infinite in width and length directions. First of all, governing partial differential equations in the spatial domain for the plate and fluid are converted as ordinary differential equations in wave number domain using Fourier transform techniques. Solutions of the ordinary differential equations are then expressed in terms of wave modes with unknown constants. Finally, these unknown constants are determined by boundary conditions on water-plate interfaces and on the interfaces between layers of the laminate. Responses in frequency domain for the fluid-loaded composite laminate are obtained with the help of inverse Fourier transform techniques. Complex path techniques are proposed to avoid singularity of integrands associated with the inverse Fourier transforms. Responses in time domain for the fluid-loaded composite laminate are found by application of the Fourier superposition method. An exponential window method is used to overcome singularity of integrands at zero and cut-off frequencies. Numerical examples are provided for steel plates and composite laminates in contact with water on one side or on two sides. The fluid effect is studied through the comparison of the computational results in the examples. It is obvious that the coupling fluid not only affects the amplitude of wave propagation in composite laminates, but also changes the distribution pattern of the response curve. It is also found that the fluid effect is strongly dependent on the frequency.