Rapid Visualization of FRP–Concrete Interfacial Defects Using Scanning Array Infrared Thermography

Externally bonded fiber-reinforced polymer (FRP) laminates are widely used to strengthen RC structures. However, interfacial defects at the FRP–concrete bonding layer can lead to reduction of strength. Therefore, to inspect these interfacial defects is essential for structural safety. This study proposed a scanning array infrared thermography (SAIRT) method aiming at rapid visualization of such defects. First, a total of 16 FRP–concrete specimens were tested using the proposed SAIRT system in static mode, which demonstrated that the system accurately identified the location, size, and shape of preset defects within 2 s at a distance of 50 cm. Second, multiphysics numerical simulation was conducted and matched well with the experimental results. The parametric study results indicate that both the thickness of the adhesive layer and the heating distance have an influence on the effectiveness of SAIRT. Finally, an FRP-strengthened RC beam was inspected using the proposed SAIRT system in scanning mode. Results showed that the system can accurately visualize the interfacial defects within areas ≥25 mm2 at a scanning speed of 10 cm/s, which outperforms existing methods in both accuracy and efficiency.