Advancing aerospace maintenance: Thermochromic liquid crystal coating method for skin-to-core disbond detection in CFRP honeycomb structures

Abstract

A novel Non-Destructive Evaluation (NDE) method for aerospace maintenance is introduced, utilizing advanced Thermochromic Liquid Crystal (TLC) ink to detect skin-to-core disbonds in carbon fiber-reinforced polymer (CFRP) honeycomb structures subjected to low-velocity impacts, representing a state-of-the-art integration of functional materials (TLC) with essential aerospace maintenance practices. Traditional NDE methods for detecting disbonds in aerospace structures often necessitate skilled technicians and sophisticated equipment. In contrast, the current study demonstrates that the proposed TLC coating method provides a straightforward, real-time detection technique that can serve as a preliminary or substitute inspection method. The detection and characterization results using the TLC coating method are rigorously evaluated through comparison with Forward-Looking Infrared (FLIR) by employing a high-performance thermal imaging camera. Results demonstrated that the TLC coating method achieved the same detection limits as FLIR thermography, with measurements of the disbond size differing by no more than 5 % between the two methods. A new heating method, Communicative Heating Thermography (CHT), was introduced for use with the TLC coating method in field applications without the need for post-processing, or expensive equipment. CHT enabled operators to dynamically adjust heat application based on real-time feedback from the TLC coating, optimizing disbond detection. This method was successfully implemented by untrained operators with an accuracy of 100 %.