Scattering Directivity Pattern Analysis of Low-frequency Lamb Wave at Sub-surface Damage in Composite Laminates

This article presents the scattering phenomena of the low-frequency zero order anti-symmetric (A0) mode Lamb wave at a sub-surface defect in composite laminates. The variable angular amplitude distribution at the defect is one of the key factors affect damage detection algorithm development, toward unavailability of the analytical model of the scattered wave. In this research, the numerical study to investigate the reflection and transmission characteristics of A0-mode Lamb wave at a subsurface defect is investigated. Cross-ply CFRP laminates with sub-surface damage of the various size of the defect were considered as the specimen. Each layer of the laminate considered as horizontally and vertically transversely isotropic material. Numerical simulation is carried out using explicit type software LS-DYNA. Low frequency Lamb wave of 30 kHz is excited by a sinusoidal toneburst. To calculate the Scattering Directivity Pattern (SDP), time dependent normal displacements are recorded. Numerical results are compared with the experimental study. This study shows that the fiber orientation of the outer laminae has a significant influence on the scattering characteristics and less impact on the size of the defect.