ULTRASONIC ATTENUATION RESULTS OF THERMOPLASTIC RESIN COMPOSITES UNDERGOING THERMAL AND FATIGUE LOADING

摘要

Measurements of the ultrasonic slope of attenuation of thermoplastic composites undergoing large numbers of flight cycles were made. After as few as 300 flight cycles, samples showed localized areas of increased attenuation for the high strain protocol. After more than 4000 cycles of thermal-mechanical loading the thermoplastic samples showed significant increases in the attenuation data for both low and high strain testing. High strain level effects on thermoplastics were demonstrably greater than from low strain levels. The slope of attenuation increases approximately linearly with number of flight cycles in the thermoplastic composites. This behavior is distinctly different from thermoset composites that show little effects of aging until after 2500 flight cycles. Finally, attenuation measurements are indicating material changes long before mechanical testing is being affected.