NDTnet 1998 Aug, Vol.3 No.8

Abstract

Lamb waves propagation has recently found a great potential for application in nondestructive testing of composite laminates, for example, in material characterization and in rapid detection of defects in large-size composite laminates [1]. As Lamb wave has to propagate through a waveguide such as the laminate plate, the information it carries is likely to be of that through the whole thickness and it is less clear whether it can be used for detail characterization of the defects, such as size and location through the thickness. Recently, it is reported that Lamb wave amplitude is sensitive to the delaminations that are close to the measuring surface of the composite laminate [2].

In this paper, Lamb waves (S_o mode) transmission over the delamination region in composite laminates was studied using numerical simulation by finite element method, and the result obtained was compared with measurement. It was found that when Lamb wave encounters a delamination, the transmitted amplitude is divided into two parts, entering the two layers that are separated by the delamination. Furthermore the measured Lamb wave amplitude is proportional to the thickness of the underlying layer. It is observed that the closer the delamination to the measuring surface is, the less the Lamb wave amplitude is measured. This agrees well with early experimental results. Since Lamb wave is most sensitive to the delamination close to the surface, it may provide some advantage for characterization of this type of defects, which is difficult for conventional normal incidence inspection. Further discussion on how to combine the Lamb wave measurement for both applications of rapid inspection and characterization of defects will be carried out.

1. Guo, N and Cawley, 1994, Mater. Eval., vol.52, 404-411.
2. Tan, K.S., Guo, N., Wong, B.S. and Tui, C.G., 1995, NDT&E Inter, vol.28, 215-227.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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