Abstract
A generation laser scanning method for visualizing ultrasound waves propagating on an object, such as composite structures, as an animation image had been developed. This method makes flaw inspections for objects to be visible, quick and easy to understand. In this research, we investigated to make the method completely contact-free by applying an air-coupled ultrasound transducer as a receiver, instead of a contact PZT transducer, and to apply it to flaw inspections of CFRP by visualizing Lamb wave propagations. First, relationships between signal amplitude and transmitting/receiving angle of air-coupled ultrasound transducers were investigated for CFRP plates with various fiber orientations. Then based on the results, the air-coupled transducer was applied as a receiver in the method, and several visualized images of A0 mode Lamb waves on CFRP with flaws, such as artificial delaminations or lack of fiber, were obtained without a contact of transducer. The flaws were successfully detected in the images. It was also shown that fiber orientation of CFRP affects the generation of Lamb wave by laser, and that single mode of Lamb waves can be visualized by adjusting receiving angle.
