Delamination Visualization in CFRP Laminated Concrete Structures Using Pulsed Laser-Based Ultrasonic Propagation Images

One of the most critical characteristics of concrete structures is the brittleness of the concrete and hence the concrete is vulnerable to tension force. To overcome this drawback, the use of carbon-fiber–reinforced polymer (CFRP) sheets and/or plates laminated on the surface of concrete structures has increased. However, the efficiency of the CFRP reinforcement to endure the tension force is reduced when the CFRP sheets and/or plates are delaminated from the concrete structures due to external loads and impacts during service. This study presents the application of a pulsed laser scanned ultrasonic wave propagation imaging technique for detecting delamination damage of the CFRP laminated concrete structures. For the experimental studies, the delamination was artificially formed when the CFRP sheets were attached on the concrete structures and scanned using the Nd: YAG pulsed laser scanning system. By applying a frequency-wavenumber filtering algorithm to the wave responses measured from the Nd: YAG pulsed laser scanning system, flaw images of the delamination of the CFRP sheets were successfully obtained. This result confirmed the feasibility of the pulsed laser scanned ultrasonic wave propagation imaging technique to serve as an effective structural health monitoring system for actual CFRP laminated concrete structures.