Interdigitated PVDF transducer for flaw detection

Since the recognition of the advantages of using Lamb Waves in nondestructive testing (NDT), Lamb Waves and other guided waves have attracted more and more attention nowadays. Unlike waves used in conventional ultrasonic inspection, such as bulk longitudinal and shear waves, which propagate in the region of structure immediately around the transmitting transducer, Lamb Waves can propagate over a long distance. Previously in our work, monolithic interdigitated PVDF transducers for generating surface acoustic waves have been built by using photolithography technology. These sensors have been tested to be able to successfully excite and receive Lamb Waves. As an extension of previous work, this paper focuses on the implementation of interdigitated PVDF sensors on some laminated structures made of carbon fiber composite materials with flaws of different sizes. Experiments have been conducted, and results from PVDF IDTs have been compared with those from PZTs. Efforts have been spent on identifying the components of Lamb waves propagated in these sample structures and evaluating the differences in the received signals.