Second Harmonic Generation of Guided Wave at Crack-Induced Debonding in FRP-Strengthened Metallic Plates

The use of fiber-reinforced polymer (FRP) has been widely recognized to be an effective and economical way to strengthen existing structures or repair damaged structures for extending their service life. This study investigates the feasibility of using nonlinear guided wave to monitor crack-induced debonding in FRP-strengthened metallic plates. The study focusses on investigating the nonlinear guided wave interaction with the crack-induced debonding. A three-dimensional (3D) finite element (FE) model is developed to simulate the crack-induced debonding in the FRP-strengthened metallic plates. The performance of using fundamental symmetric ([Formula: see text] and anti-symmetric ([Formula: see text] modes of guided wave as incident wave in the second harmonic generation at the crack-induced debonding is investigated in detail. It is found that the amplitude of the second harmonic and its variation with different damage sizes are very different when using [Formula: see text] and [Formula: see text] guided wave as the incident wave, respectively. The results suggest that it is possible to detect potential damage and distinguish its type based on the features of the generated second harmonic.