WAVE MOTION IN A 3-LAYERED, ORTHOTROPIC ISOTROPIC ORTHOTROPIC, COMPOSITE SHELL

A classification of the possible free wave motions in a three-layered composite thick cylinder is presented. The governing equations of moti on for free wave motion for isotropic and orthotropic elastic media ar e given and a combined solution is developed for a thick cylinder made of three different materials, such as ortho tropic-isotropic-orthotro pic layers. The use of Bessel and special Frobenius series is required to obtain a correct, closed form solution for the propagating waves. Numerical results are given in the form of dispersion curves and these are discussed. A correct approach to the calculation of the cut-off f requencies is presented. It is shown that the wave speeds of decoupled longitudinal-shear motion in orthotropic shells is dependent upon the ratio of the different shear moduli, C-i66/C-i55. The influence of a thin, soft rubbery material at the centre of a sandwich configuration is thoroughly analyzed. The effect of the isotropic core properties (i ts stiffness and thickness) on the dynamics of the wave motion is inve stigated.