Enhancing non-destructive detection and localization of interfacial debonding in FRP concrete composite beams

This study introduces a baseline-free nonlinear guided wave technique for detecting and localizing debonding in FRP-concrete composite beams. The method is cost-effective and advantageous over conventional localization approaches, as it can detect and locate debonding using only two sensors. Both pulse-echo and pitch-catch configurations were evaluated through experiments and finite element simulations. Results demonstrated that the pulse-echo configuration provided accurate localization of debonding, with a relatively small error compared to the actual defect location. In contrast, the pitch-catch configuration yielded stronger nonlinear responses, making it more effective for damage detection due to the higher nonlinear amplitude observed. However, accurate localization using pitch-catch requires careful frequency selection, as velocity differences between wave modes significantly influence localization reliability. The technique successfully identified and localized small debondings, with improved accuracy for larger and deeper defects. The effects of debonding depth and size on localization accuracy were also examined, confirming that both parameters substantially influence the results. These findings demonstrate the potential of this approach for structural health monitoring of FRP-retrofitted concrete structures.