Debonding growth evaluation in CFRP-reinforced steel structures based on correlation analysis using guided waves

Externally bonded carbon fibre reinforced polymer (CFRP) reinforcement is becoming increasingly popular in the field of structural retrofitting due to its considerable efficiency. However, debonding failure occurs sometimes at the interface between CFRP and steel substrate, which is found to be fatal for the CFRP-reinforced structures. Thus, the bonding condition between two materials should be closely monitored to ensure structural serviceability. A linear guided wave based method employing the correlation analysis is adopted in this paper to monitor the growth of debonding failure generated by fatigue in a CFRP-strengthened steel structure from a relatively small scale (smaller than 20 mm in diameter). The correlation coefficients (CC) between the benchmark signals and the signals after certain cycles of loading are calculated individually. Subsequently, the damage index (DI) is extracted on the basis of CC to illustrate the extent of debonding. Finally, the possible debonding position in the structure is predicted by a probability based imaging method.