Mode Conversion and Scattering of Lamb Waves at Delaminations in Composite Laminates

This paper presents a study of Lamb wave scattering and mode conversion at a delamination in quasi-isotropic (QI) composite laminates. The study employs the fundamental antisymmetric mode (A(0)) Lamb wave as the incident wave and investigates the A(0) scattered Lamb wave and mode converted fundamental symmetric mode (S-0) Lamb wave (A(0)-S-0) at the delamination. A three-dimensional (3D) explicit finite-element (FE) model is proposed to predict the Lamb wave propagation in the QI composite laminates, and A(0) scattered wave and A(0)-S-0 mode converted wave at the delamination. An experimental study is also carried out to demonstrate that the 3D FE model is able to provide a reasonable prediction of the A(0) and S-0 Lamb wave propagation in the QI composite laminates. The results show that the amplitudes of the A(0) scattered and A(0)-S-0 mode converted Lamb waves depend on the fiber orientation of the outer laminae, and the size and through-thickness location of the delamination. In summary, the results of this study can further advance the delamination detection techniques using Lamb wave and gain physical insights into the scattering and mode conversion of Lamb wave at the delamination. (c) 2019 American Society of Civil Engineers.