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Multilayered composite materials are being studied extensively for implementation in flywheel systems for the International Space Station (ISS). Rotor standard sections have been developed to determine damage tolerance levels of the multilayered composite materials in these flywheel systems. Four such rotor sections with simulated delaminations, foreign material inserts, and notches were investigated with a recently developed ultrasonic spectroscopy technique. The ultrasonic system employs a continuous swept sine waveform and performs an FFT on the frequency spectrum. In addition, the system is capable of equalizing the amount of energy at each frequency. Equalization of the frequency spectrum, along with interpretation of the second FFT aids in the evaluation of the spectrum resonance spacing, or fundamental frequency. The ultrasonic responses from defect free regions of the multilayered rotor sections are compared with responses from regions with simulated delaminations, foreign material inserts, and notches to establish the potential of this nondestructive evaluation (NDE) method for the evaluation of flywheel rotor systems.
composite materials, flywheel rotors, resonance, ultrasonic spectroscopy
Research Scientist, Cleveland State University, Cleveland, OH
Senior Scientist and NDE Group Leader, NASA Glenn Research Center, Cleveland, OH