Effect of Ply Orientation on Nonlinear Lamb Wave Delamination Interactions in GFRP Composite Laminates

Abstract

AbstractLaminated composite plates are widely used in many engineering applications. In order to ensure safety and reliability of such laminated composite structure, various nondestructive testing (NDT) techniques are used. Lately, Lamb waves-based methods have been explored for their use in NDT of composite laminates, as they offer an optimum combination of the area scanned and damage sensitivity. Techniques based on nonlinear interactions of Lamb waves with damage further increase the damage sensitivity when compared with their linear counterparts. However, most of these studies are concerned with unidirectional laminates. Although the effect of ply orientation on the linear interaction has been reported recently, the effect of ply orientation on the nonlinear interaction of the Lamb waves with breathing behaviour of delamination has not been addressed yet. In this regard, this study reports the effect of ply orientation on the generation of higher harmonics. This work deals with the nonlinear interactions of A0 Lamb mode with delamination in an eight-layer GFRP composite plate, numerically. Further, a thorough parametric study is performed for assessing the impact of ply orientations and inter-laminar position of the delamination on the nonlinearity index. The investigation also suggests that the ply orientation plays an important role in determining the wave speed, the trend which proportionally matches with the nonlinearity index. Therefore, this analysis can prove to be useful in arriving at a strategy to characterize and localize the delamination in laminated composite plate, with various layup sequences.KeywordsComposite laminatePly orientationFundamental A0 Lamb modeHigher harmonics