An exact analytical solution for a three-dimensional case of the vibration of an infinite orthotropic plate loaded on its upper boundary is considered. The influence of source parameters on the characteristics of wave propagation in an orthotropic elastic infinite plate are analyzed. An asymptotic approximation for evaluating displacement in the far field is developed. Sample numerical calculation results are presented for various source parameters.

Ultrasonic spectroscopy is introduced as a test procedure for nondestructively evaluating composite materials. Tests reported in this study show that it is possible to locate flaw areas in a composite tube with both ultrasonic C-scan and ultrasonic spectroscopy procedures. In particular, the purpose of this paper is not to present quantitative comparisons of theoretical and experimental results of ultrasonic wave propagation in composite tubes but to indicate that frequency signatures obtained from ultrasonic spectroscopy can be useful in nondestructively evaluating composite materials. A theoretical sample problem is presented that demonstrates the sensitivity of the spectroscopy method in detecting pulse spreading. Experiments on two composite tubes are also presented to show the difference in frequency signatures that occurs when comparing flaw and no flaw areas in a structure. The major advantage of this method compared to conventional ultrasonic methods lies in its ability to detect precisely pulse dispersion and pulse location in the time domain. The frequency signature approach represents an alternative approach to standard ultrasonic pulse echo and through transmission signal analysis that often proves useful when standard methods of analysis fail because of poor resolution and lack of basic understanding and interpretation.

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