VISUALIZATION OF WATER INGRESS IN ALUMINIUM HONEYCOMB SANDWICH PANEL THROUGH MODE ISOLATION OF LAMB WAVEFIELD

Abstract

Water ingress into the honeycomb cells of aerospace structures can compromise the aircraft’s safety and performance. Due to this reason, detecting it as soon as possible is critical. Even though the effectiveness of guided ultrasonic wavefield propagation imaging (G-UPI) in detecting various types of damage with high resolution has already been well-demonstrated, its capability in detecting water ingress in honeycomb cells has not been investigated. In view of this, the aim of this study is to investigate the feasibility of using G-UPI to detect and visualize water ingress in the honeycomb cells by inspecting an aluminum honeycomb sandwich panel with simulated water ingress in six individual cells. Based on the results, it has been shown that isolating the A0 mode of the waves can significantly improve the visibility of the water-filled cells. Moreover, the quantitative comparison of three different visualization methods, i.e., ultrasonic energy mapping (UEM), dominant frequency amplitude mapping (DFAM), and spectral energy mapping (SEM), has revealed that SEM is the best visualization method due to its 7.2 and 1.5 times higher contrast compared to UEM and DFAM, respectively. All in all, G-UPI has been shown to be able to effectively detect water ingress. However, careful selection of a suitable wave mode and image generation algorithm is required to achieve optimal results.