Flaw detection in Multi-layer, Multi-material Composites by Resonance Imaging: utilizing Air-coupled Ultrasonics and Finite Element Modeling
Ceramic tiles are the main ingredient of a multi–material, multi–layered composite being considered for the modernization of tank armors. The high stiffness, low attenuation, and precise dimensions of these uniform tiles make them remarkable resonators when driven to vibrate. Defects in the tile, during manufacture or after usage, are expected to change the resonance frequencies and resonance images of the tile. The comparison of the resonance frequencies and resonance images of a pristine tile/lay–up to a defective tile/lay–up will thus be a quantitative damage metric. By examining the vibrational behavior of these tiles and the composite lay–up with Finite Element Modeling and analytical plate vibration equations, the development of a new Nondestructive Evaluation technique is possible. This study examines the development of the Air–Coupled Ultrasonic Resonance Imaging technique as applied to a hexagonal ceramic tile and a multi–material, multi–layered composite.