Feasibility of using Lamb waves for corrosion detection in layered aluminium aircraft structures

Corrosion is one of the major causes for the structural failure of an airframe. Assessment of corrosion in layered aircraft structures is thus an important issue in nondestructive evaluation for the airworthiness of aircraft. Advantage can be taken of the thickness-dependent propagation properties of Lamb waves to detect and characterize material thinning due to corrosion. Amplitude and time-of-flight measurements using Lamb waves were performed on laboratory-fabricated aluminum specimens consisting of: single and double layers of various thickness, 5% to 22% of machine-milled and chemically-induced material loss. Analysis and comparison of the results of these tests have led to further understanding of the wave propagation behavior in corroded areas and allow the estimation of the percentage of corrosion-induced material loss