Leaky Lamb Waves (LLW) in Multiorientation Composite Laminates

Abstract

Considerable efforts have been made in recent years to develop quantitative nondestruc- tive evaluation (NDE) techniques for composite materials, which are being used increasingly in primary structures. The leaky Lamb wave phenomenon has shown considerable potential as an NDE method [1]. Most results reported in this area to date have been concerned with unidirectional laminates [2-4]. This is attributed to the complexity involved in theoretically predicting the response of these materials, as well as to certain difficulties associated with the experimental research. In practice, structural composites are made up of layers in vari- ous orientations. Their stacking order is dependent upon the requirements of the particular application. Therefore, the capability of analyzing the behavior of Lamb waves in multi- orientation laminates is crucial for the application of LLW to composites. In recent years, the authors have made significant progress in the areas of data acquisi- tion for LLW experiments and in the theoretical analysis of the LLW phenomenon. Further, they have developed a data inversion technique for determining the elastic constants and interface properties of composite laminates [5,6]. This has led to better capability for com- paring theoretical and experimental results for general laminates. The theoretical model accounts for attenuation in the composite as well as for the presence of matrix-rich layers between the laminae. In this paper, our progress in the areas of theoretical and experimental research on guided wave propagation in general multiorientation laminates is described.