Radome health management based on synthesized impact detection, laser ultrasonic spectral imaging, and wavelet-transformed ultrasonic propagation imaging methods

Abstract

A radome must not only withstand various forces during operation, but also provide a window for electromagnetic signals. A radome is generally a composite sandwich structure. Much of the damage to radomes is barely visible to the naked eye on the outer surface, but is severe internally. In this study, a radome health management strategy consisting of in-flight damage event detection and ground damage evaluation processes is proposed. A radome health management system, composed of an on-board subsystem and a ground subsystem, was developed to realize the strategy. An in-flight event detection system was developed based on acoustic emission (AE) technology. A built-in amplifier-integrated PZT sensor was used, and the minimum impact energy that the on-board subsystem can detect was determined. The AE sensor was then switched to an ultrasonic receiver. A scanning laser ultrasonic technology was combined with the ultrasonic receiver to develop a ground nondestructive evaluation subsystem. For in situ damage visualization, laser ultrasonic frequency tomography and wavelet-transformed ultrasonic propagation imaging algorithms were developed in this study. To demonstrate the robustness of the ground subsystem, a damage was generated by 5.42 J impact in a glass/epoxy radome with honeycomb core, and the impact image of 25 mm in diameter invisible outside could be visualized with the combination of ultrasonic spectral imaging (USI) and wavelet-transformed ultrasonic propagation imaging (WUPI), which made the propagation of only the damage-related ultrasonic modes visible.