Quick inspection of impact-induced delamination in cross-ply laminate by the use of Lamb waves

Composite laminates are valuable structural components for aircraft and spacecraft because of their superior specific strength and stiffness. However, damage detection is difficult in composite laminates due to the anisotropy of the materials and the fact that much of the damage often occurs beneath the top surface. Internal damage from impact is the most prevalent type of damage for composite laminates. This internal damage, in the form of matrix cracks and delamination, can cause significant loss of strength or stiffness. Therefore, delamination inspection has been a subject of considerable interest. We propose in this paper a quick inspection technique, consisting of two line scans, for impact-induced delamination by the use of Lamb waves. The first scan measures the S0 mode velocity before and after impact and quantitatively evaluates the delamination size. The second scan then measures the maximum amplitude of the detected signal in line, including the delamination, and determines the location of the delamination edge. A conventional C-scan was performed to validate this method, and we confirmed that this method has powerful potential for quick inspection for impact-induced delamination.