QUANTITATIVE MATERIALS CHARACTERIZATION USING AIR-COUPLED LEAKY LAMB WAVES

Air-coupled ultrasonic materials characterization has been accomplishe d in composite plates through accurate reconstruction of the transmiss ion coefficient using leaky guided waves. The spatial and frequency de pendencies of the transmitted leaky waves have been measured for a var iety of composite plates including aluminum-aramid and graphite-epoxy. Furthermore, a general method has been introduced to reconstruct the transmission coefficient experimentally from a one-dimensional transdu cer position scan, obtaining a synthetic focused aperture by summing m easured signals for many transmitter-receiver separations and transduc er incident angles. These results have been employed to deduce, with h igh precision, the transmission coalescents of the plate over the freq uency and angular bandwidths covered by the measurements. The high deg ree of accuracy in the measured transmission coefficient has been expl oited to construct an efficient inversion algorithm to estimate the vi scoelastic material properties and/or sample thickness.