Numerical Analysis of Lamb Wave Propagation in Delaminated Composite Laminate

Abstract

The paper deals with the numerical modelling of propagation of ultrasonic Lamb wave and its interaction with delamination in a composite laminate. The interaction of the fundamental anti-symmetric Lamb mode (Ao) with a structural discontinuity viz. semi-infinite delamination in a Glass Fiber Reinforced Plastic (GFRP) composite laminate was studied through numerical modelling carried using Finite Element Method (FEM). When Ao mode interacts with the front edge of a delamination-the reflection, transmission and also generation of fundamental symmetric Lamb mode (So) into the sub-laminates takes place. The incident Ao and generated So modes propagate in the sub-laminates as AoAo and AoSo modes. The arrival times of AoAo and AoSo modes at receiving points were calculated analytically and compared with those obtained from numerical simulations. Further, power transmission coefficients of various Lamb modes (AoAo and AoSo) propagating in the top and bottom sub-laminates were estimated through numerical simulations. It is observed that the power transmission coefficients of AoAo mode are independent of the frequencies of excitation 200kHz and 225kHz, whereas that of AoSo mode depends. Furthermore, it was found that the transmission coefficients of AoAo and AoSo modes depend on the location of delamination across the thickness.