Propagation of Ao mode through the front edge of a delamination: Numerical and experimental studies

Abstract

Numerical and experimental studies carried out on the propagation of ultrasonic Lamb wave and its interaction with the front edge of a delamination in a cross-ply and unidirectional composite laminates are presented in this paper. When the fundamental antisymmetric Lamb mode (Ao) is incident at the leading (front) edge of a delamination, it undergoes reflection and transmission into the sub-laminates. Numerical simulations carried out on the interaction of the Ao mode with the edge of a semi-infinite delamination revealed that during this interaction, So mode is generated and propagate as AoSo (propagation of the So mode due to the incident Ao mode) mode in the top and bottom sub-laminates along with the incident Ao mode, which propagates as AoAo (propagation of the Ao mode due to the incident Ao mode) mode. Transmission factors and power transmission coefficients of AoAo and AoSo modes on an assortment of excitation frequencies — 150 kHz, 175 kHz, 200 kHz and 225 kHz, and thickness ratios were computed. Experimental validation of results arrived through numerical simulations, was also carried out employing air-coupled ultrasonic transducers.