Development of hybrid one-dimensional finite element/analytical method for analysis of Lamb wave propagation characteristics in composite panels

The objective is to develop a hybrid one-dimensional finite element (FE)/analytical method to analyze the Lamb Wave propagation characteristics in a composite panel for the purpose of detecting the specific structural defects in the composite panel. Here, it is proposed to use a composite panel using a finite element approximation in the thickness direction while wave solutions are assumed in the plane directions. Thus, it makes possible to use the small number of finite elements even for ultrasonic frequency analysis in computationally efficient manner. By solving the eigenvalue problem of the resulting hybrid FE/analytical matrix equation, the dispersion relations of the Lamb waves propagating in composite panels can be calculated in wave number/frequency domain. The resulting dispersion relations can be then used to determine the frequency, wavelength, and wave speed of a specific Lamb wave. In order to validate the proposed method, the Lamb wave speeds of a aluminum panel are calculated by using a conventional, analytical method and the proposed method. It is shown that the Lamb wave speeds obtained by using the proposed method agree well with the speeds calculated by using the analytical method.