Lamb wave method for quick inspection of impact-induced delamination in composite laminates

This paper proposes a new inspection technique using Lamb waves to detect impact-induced delamination in composite laminates. The technique, which consists of two line scans, is as follows. The first scan measures the arrival times of the transmitted S0 mode along the 0° direction to detect delamination and evaluate its size. The second scan measures the maximum amplitude of the earliest wave packet in a line, including the longest delamination, to locate its edge. We performed this technique on impacted CFRP cross-ply laminates. A remarkable decrease in the arrival times due to the delamination is detected, and the delamination length can be calculated based on a simple model for Lamb-wave propagation. Furthermore, the delamination edge is located as a sudden decrease in the amplitude. The technique enables detecting the delamination and evaluating its size and location using only the two scans. We demonstrated the validity and usefulness of this technique.