Detection of Debonding Between Fiber Reinforced Polymer Bar and Concrete Structure Using Piezoceramic Transducers and Wavelet Packet Analysis

Fiber reinforced polymer (FRP), a composite material with high corrosion resistance and high strength-toweight ratio, has been increasingly used in reinforced concrete structures. The effectiveness of the structures depends on the bonding behavior between FRP composites and concrete structures. Therefore, detection of the debonding between the FRP materials and the hosting concrete structure is of great importance to ensure the structural safety. This paper proposes a stress wave-based active sensing approach to monitor the debonding process of FRP bar with the hosting concrete structure. One shear-type lead zirconate titanate (PZT) patch bonded on the outer surface of the FRP bar was used as an actuator to generate stress wave. Two smart aggregates (SAs), which were fabricated by sandwiching a shear type PZT patch between two protection marble pieces, were embedded in the hosting concrete structure to detect the wave response. The occurrence of debonding between the FRP bar and the hosting concrete structure attenuates the wave propagation. An FRP bar reinforced concrete specimen was designed and fabricated in laboratory. A pullout test was conducted to simulate different degrees of debonding damage. The attenuation of the stress wave due to debonding was clearly observed from the signal received by SAs in both time and frequency domain. Furthermore, a damage index based on wavelet packet analysis was developed to evaluate the debonding status. Experimental results demonstrate that the proposed method has potentials to detect different degrees of debonding damage of FRP bar reinforced concrete composite structures.