Scattering analysis of fundamental anti-symmetric Lamb wave at delaminations in composite laminates

Abstract

This study focuses on the three-dimensional (3D) scattering characteristics of the fundamental anti-symmetric (A0) Lamb wave at a delamination in composite laminates. The understanding of the scattering characteristics plays an important role in the application of Lamb wave based damage detection techniques. One critical factor affecting the performance of Lamb wave based damage detection techniques is the angular distribution of the scattered wave amplitudes at the delamination. Analytical solutions for this problem do not exist due to the anisotropic nature and multilayer characteristics of composite laminates. This paper employs a 3D finite element (FE) method to analyse the A0 mode Lamb wave scattering characteristics at delaminations. Good agreement is found between the simulations and experimental measurements. Extended parameter studies show that the angular distribution of the scattered wave amplitudes depends on the stacking sequence of the laminates, the damage size to wavelength ratio and the through-thickness location of delamination. The results of these studies provide improved physical insight into the scattering phenomena at a delamination, which can be used to validate and improve the performance of Lamb wave based damage detection methods by selecting transducer locations and excitation frequency. The study also investigates the feasibility of simulating delamination damage by bonding masses to the surface of composite laminates for Lamb wave based damage detection and characterisation methodologies verification. The results suggest that simulating delamination damage by bonded masses requires careful design and is not as straight forward as suggested in the literature.