Guided waves for debonding identification in CFRP-reinforced concrete beams

Ultrasonic guided waves excited and sensed by surface-bonded piezoelectric wafers were simulated and used to quantitatively evaluate the debonding between concrete beams and carbon fibre reinforced polymer (CFRP) overlay. Eight concrete specimens reinforced by composite overlay were prepared with different bonding conditions, which were simulated by inserting different sizes of Teflon films when the overlay was cured. A continuous wavelet transform based signal processing method was implemented to filter out broad-band environmental noise in the experiments. In consideration of the inevitable discrepancies in different specimens due to concrete preparation and sensor installation, a time-reversal process was applied to individual specimens to achieve self-comparison between the originally emitted and reconstructed wave signals which were sent back to the actuator. That procedure highlighted discrepancies in specimens, caused by different debonding conditions. Debonding indices were successfully calculated to quantify the severity of debonding, showing the potential of guided waves for integrity evaluation of CFRP-reinforced concrete structures.