Guided wave based debonding detection in CFRP-reinforced steel structures

Carbon fibre reinforcement polymer (CFRP) has proved to be effective in strengthening the ageing steel structures due to its outstanding properties. However, the debonding problem, which may occur at the interface during the installation stage or service life, will highly influence the performance of the retrofitted structures. In this paper, to achieve the detection of debonding, numerical simulation was first performed to verify the feasibility of guided wave based structural health monitoring (SHM) method. FRP-reinforced steel plates with different sizes of debonding were simulated where surface mounted piezoelectric (PZT) wafers were employed to excite and collect the signals. The incident wave was chosen to be the anti-symmetrical mode, which is more sensitive to debonding because of its dominant out-of-plane motion. The time-of-flight (ToF) of the first arriving wave package in the received signals was extracted from the time domain. The simulation results indicated that the ToF decreases linearly with the increase of debonding size. The corresponding experiment was then carried out to verify the simulation results and a similar trend was obtained.