3D finite element prediction of scattering and mode conversion of lamb waves at delaminations in composite laminates

Abstract

Detection of damage using Lamb wave has attracted significant attention in the last decade. It has been shown that Lamb wave is sensitive to most types of damages, efficient in detecting small and subsurface damage, and able to inspect large area. However, the capability and sensitivity of Lamb wave on detecting delaminations in composite laminates, especially the mode conversion effect, have not yet been fully investigated, which limits quantitative characterization of the delaminations. This study presents a three-dimensional (3D) finite element (FE) simulation of the fundamental anti-symmetric mode (A0) Lamb wave scattering and mode conversion from A0 to fundamental symmetric mode (S0) Lamb wave at the delamination in composite laminates. The 3D FE simulation is first validated using experimentally measured data, such as group velocity and amplitude of the incident Lamb wave in different wave propagation directions. There is good agreement between the FE calculated and experimentally measured results. The 3D FE model is then employed to predict the A0 scattered Lamb wave and mode conversion from A0 to S0 Lamb wave, which provides understanding about the scattering and mode conversion phenomenon of Lamb wave at the delaminations.