Ultrasonic Non-Destructive Testing of Composite Materials.

This final technical report summarizes the work completed on a project utilizing ultrasonic wave dispersion, frequency-dependent velocities and attenuation measurements in a variety of composite materials. The report summarizes various measurement techniques and makes a critical comparison between the results obtained using each of the techniques on various composite specimens and pure epoxy matrix only. The use of such measurements as a technique for monitoring the microstructural changes accompanying the mechanical deformations and thermal cyclings of a composite specimen is investigated. The measurements from 1 to 10 MHz clearly show an increase in attenuation, however, the variation from specimen to specimen and between the values obtained with the various techniques is greater than the microstructurally induced attenuation changes. The effects on the dispersion curve and the frequency-dependent velocity data is less than the variation measured from specimen to specimen. Author