Experimental and numerical research of debonding defects detection in fiber metal laminates using low-power ultrasonic-induced thermography

Debonding defects in fiber metal laminates (FMLs) pose a significant threat to structural reliability, necessitating efficient and non-destructive inspection methods. This study explores the use of low-power ultrasonic-induced thermography (LUIT) for rapid visualization of debonding defects in FMLs through combined experimental and numerical investigations. An inspection system was developed, incorporating bispectral analysis for the determination of optimized excitation frequencies, thereby enhancing the heat generated at defect locations to achieve improved detection performance. Infrared thermography was employed to monitor transient temperature evolution, and a contrast-based time-slice selection strategy was introduced to enhance defect visibility. Furthermore, a comprehensive numerical simulation framework integrating modal analysis, implicit dynamic simulation, and thermo-mechanical coupling was proposed to reveal the underlying heating mechanisms, focusing on frictional dissipation, viscoelastic damping, and plastic deformation. The combined results demonstrate the capability of LUIT to selectively heat debonding defects without damaging the material, with defect detectability strongly influenced by defect size, depth, and excitation timing. The findings demonstrate that LUIT offers a fast, safe, and non-destructive approach for reliable debonding defect detection in FML structures.