Ultrasonic Reflection and Wave Propagation in Multilayered Composite Plates

This paper presents selected results of numerous ultrasonic reflection measurements on plates of laminated composites in which the angle of incidence of the acoustic wave and its frequency have been varied. These measurements have been carried out on biaxially laminated graphite-epoxy specimens utilizing water as a fluid coupling medium. The stacking sequence of the samples investigated is restricted to the case of 0–90° lamination. The data are compared to the results of a recent theoretical analysis based on an exact analytical treatment of wave propagation in a fluid-coupled orthotropic plate in conjunction with a transfer matrix approach. Reflection and transmission coefficients are derived for the multilayer anisotropic laminate from which the characteristic behavior of the system is identified. In general, very good agreement is found between prediction and experiment. Moreover, significant changes in the reflection spectra are observed and predicted, depending on the orientation of the composite plates