Propagation of the Fundamental Symmetric Lamb Mode in a Symmetrically Delaminated Composite Laminate

In this paper, a study on the propagation of the fundamental symmetric Lamb mode (S_o) in a symmetrically delaminated glass/epoxy composite laminate is presented. It was found that when S_o mode is incident at the front and rear edges of a symmetric delamination, it generates A_o mode. This mode is exclusively confined to the sub-laminates. It was also observed that, during the interaction of the generated A_o mode with the edges of delamination, it, in turn generates S_o mode. Thus, S_o mode and mode converted Lamb modes undergo multiple mode conversions in the sub-laminates. The only mode that propagates in the main laminate is S_o. A signal-processing scheme based on the time-frequency spectrographic analysis was utilized to identify the wave groups propagating in the main and sub-laminates.