Effects of Delamination on Higher Harmonics Generation in Unidirectional GFRP Laminate

Abstract

AbstractWave-based damage detection of composite laminate has been a topic of significant interest for many researchers. Conventional wave damage interaction relies on the baseline approach (i.e., linear Lamb wave technique resulting in wave amplitude, wave velocity, reflection, transmission, and mode conversion). The techniques based on the nonlinear Lamb wave damage interactions have attracted significant attention in recent years. Past investigations have dealt predominantly with classical nonlinearity raised from material nonlinearity. However, non-classical nonlinearity has arisen from the contact acoustic interaction between the delamination surfaces. Delamination is the most predominant mode of failure in laminated composites. Lamb wave excitation with delamination generates higher harmonics to be used as a feasible damage indicator. Toward this, a numerical method dealing with nonlinear interactions of fundamental anti-symmetric Lamb mode with single and multiple delaminations in an eight-layer GFRP-laminated composite plate is investigated using ANSYS. The effective nonlinear Lamb wave parameters (nonlinearity index) are extracted to characterize the effects of multiple delaminations. Further, the effect of overlapping delaminations on the nonlinearity index is also analyzed. The study suggests that the nonlinearity index increases due to the increment in the overlap between two delaminations.KeywordsComposite laminatesMultiple delaminationsLamb waveHigher harmonics