Layer‐Specific Fatigue Damage Monitoring of <scp>GLARE</scp> Laminates Using Buckypaper Sensors

ABSTRACT Glass laminate aluminum reinforced epoxy (GLARE) is widely used in aerospace structures owing to its excellent damage tolerance. In this study, buckypaper (BP) sensors were embedded at the surface, aluminum/fiber interface, and fiber interlaminar of GLARE 2A 2/1‐0.5 laminates to achieve layer‐specific damage monitoring under static tension, cyclic loading, fatigue, crack propagation, and post‐impact tensile conditions. The embedded sensors caused negligible mechanical degradation, with the ultimate load and displacement differing by only 0.5% and 2.1%, respectively, from those of pristine laminates. Under cyclic loading (3, 6, and 9 kN), all sensors exhibited stable and repeatable electromechanical responses. During fatigue loading (8 kN, 2 Hz, 4000 cycles), the surface sensor maintained a stable resistance variation within ΔR/R₀ = 0–0.004, while interface and interlaminar sensors showed progressive increases associated with damage accumulation. During fatigue crack propagation, the surface sensor distinguished crack initiation, stable growth, and unstable propagation with characteristic ΔR/R₀ values of approximately 0.1%, 0.32%, and 1.38%, respectively, whereas the interface and interlaminar sensors reached maximum resistance changes of 0.8% and 0.02%. After low‐velocity impacts of 2.4, 3.6, and 4.8 J, the sensors successfully detected impact‐induced damage, and post‐impact tensile tests revealed a 10% reduction in residual tensile strength. These results demonstrate that embedded BP sensors provide reliable layer‐specific identification of strain evolution, delamination, fatigue crack propagation, and impact damage with minimal influence on the mechanical performance of GLARE laminates, offering an effective strategy for in situ structural health monitoring of advanced fiber‐metal laminates.