IN1RODUCTION In the course of processing and use of modern composites it is desireable to be able to detennine estimates of their elastic properties. Elastic property infonnation available during processing could be used to detennine the state of cure of a composite. This would make possible feedback control of the cure process, thus helping to insure unifonn materials. Knowledge of the elastic properties over time of in-use structures such as aircraft, marine, and rocket motor components would

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... also allow quantitative health monitoring of these critical devices. Existing ultrasonic methods of elastic property detennination typically rely on multiple measurements at various orientations and angles of incidence. These methods are acceptable for research purposes but are impractical for routine implementation as part of a processing or inspection system. We have developed an ultrasonic technique capable of real-time estimation of elastic properties. The technique utilizes point source excitation and an array of point receivers. The frrst arrival of energy is the measured quantity. This is a relatively simple and robust measurement.