ラム波スペクトラム解析によるFRP積層板の衝撃損傷検出

概要

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A new technique using Lamb waves has been proposed to detect impact damages in FRP laminates nondestructively. Conventional ultrasonic testing such as C-scan requires two-dimensional scanning for whole area inspection because the inspected area by one operation is relatively small. In this study, for quick detection of a localized defect, spectrum analysis of Lamb waves is demonstrated. Instead of wave velocity or attenuation, acousto-ultrasonic parameters (AU parameters), which are based on the amplitude spectrum of the broadband signal, are introduced to improve the precision of the inspection. Among the several AU parameters, A2 and A4/A3 parameters, which represent the centroid and the torsion of the spectral density curve respectively, are found to be more useful to identify a localized defect in laminated composite plates. It is also found that the inspection accuracy depends on the wave propagation direction reflecting to the scattering of higher frequency waves, and can be improved by use of burst waves.