Delamination Detection and Investigation at Far-Field in Glare Laminates Using Lamb Waves

For aerospace applications, Glass-Reinforced Aluminum Laminate (GLARE) Fiber Metal Laminate (FML) presents a compelling advantage over conventional aluminum alloys due to its superior strength-to-weight ratio, tailorable mechanical properties, and resistance to fatigue and corrosion. GLARE consists of alternating layers of thin aluminum and glass fiber-reinforced prepregs. Unlike conventional materials, GLARE is vulnerable to internal damage during fabrication and operation. Nondestructive testing of large-scale GLARE structures remains challenging. This work investigates the use of guided waves for GLARE inspection, focusing on interlaminar delamination and insights into wave propagation. We assessed the effectiveness of the fundamental antisymmetric A0 mode in detecting delamination in two types of GLARE composites: GLARE 1 (Al/0 degrees/Al/0 degrees/Al/0 degrees/Al/0 degrees/Al) and GLARE 5 (Al/0 degrees/Al/90 degrees/Al/90 degrees/Al/0 degrees/Al). A numerical 2D finite-element (FE) model was created in ABAQUS CAE to analyze wave propagation in GLARE. Results show that the A0 mode was sensitive to delamination in both types of GLARES FML studied. Additionally, geometrical measurements of delamination were obtained from wave energy trapping, and positional information of delamination was obtained from the analysis of reflected waves in the reflection regime. The displacement wave field captures in TSL and BSL reveal the interfaces for low and high transmission that are found to be strongly tied with the delamination position and dispersion. At the entry and exit, the A0 Lamb wave behaves differently and experiences multi-point acoustically mismatched interaction, making the signal processing of its propagation challenging.