Detection of delamination in composite laminates using Lamb wave based nonlinear method

In this study, a Lamb wave based nonlinear method is used to detect delamination in a composite laminate. For this purpose, an artificial delamination is created in a composite laminate using a thin Teflon sheet. The research includes an experimental study as well as finite element simulation. Two higher harmonics are observed in the Lamb wave response as a result of contact nonlinearity at the delamination. A spectral damage index is extracted from the spectral information of the fundamental and higher harmonics. It is found to be invariant to the sensor location and its values show decreasing trend with increase in the delamination width. Further, a new hybrid method is introduced, wherein the spectral and temporal data are used together in order to locate a delamination.