Delamination detection in composite beams using pure Lamb mode generated by air-coupled ultrasonic transducer

The interaction of Lamb wave A ₀ mode with delamination and delamination detection in 16-ply carbon fiber–reinforced epoxy composite beams are investigated through three-dimensional finite element simulation and experimental studies in this article. Wave propagation in composite beams with delamination with different lengths and located at different interfaces are investigated in finite element simulations, and some unique mechanisms of interaction between A ₀ mode and delamination are revealed in detail. Experimental results obtained with air-coupled ultrasonic transducers are well in accordance with finite element simulation results. In an experimental study, an air-coupled ultrasonic transducer is oriented at a coincidence angle such that it generates a pure fundamental antisymmetric Lamb wave mode A ₀ for delamination detection in laminated composite beams. The receiving transducer can be oriented either to detect the transmitted wave propagating in the same direction as incident wave or to detect the reflected wave in contrast to incident wave. The location and size of delamination can be evaluated quantitatively using the time-of-flight of reflected wave from both ends of the delamination.