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This paper explores the use of ultrasonic dispersion measurements as a useful nondestructive testing tool for composite materials. The various methods for measuring the dispersion of ultrasonic waves are reviewed, including a new continuous-wave technique and the method of ultrasonic phase spectroscopy. Detailed measurements in various directions of unidirectional boron/epoxy specimens are described. Also shown are measurements in graphite/epoxy, 3D quartz/phenolic, and 3D carbon/phenolic. Application of dispersion measurements to characterize the moisture absorption and void content in boron/epoxy and graphite/epoxy specimens is reported. It appears that in cases where there is pronounced dispersion, measurements of it are sensitive to microstructural changes.
composite materials, characterization, boron/epoxy, nondestructive tests, ultrasonic wavespeeds, dispersion, phase velocity, group velocity, ultrasonic phase spectroscopy
Associate professor, Cornell University, Ithaca, N. Y.
AVCO, Wilmington, Mass.
Regional Conference of Historical Agencies, Manlius, N.Y.