Numerical and experimental investigation on debonding detection in honeycomb sandwich using air-coupled local defect resonance and coda wave analysis

Non-contact ultrasonic testing of debonding in honeycomb sandwich structure has been a major challenge in industry. In this study, the air-coupled local defect resonance (LDR) technique with coda wave analysis is proposed for nondestructive testing (NDT) of debonding in honeycomb sandwich structure. Numerical simulations have been conducted to visualize the LDR behavior of debonding in honeycomb sandwich structure by air-coupled excitations, and a decorrelation analysis method is proposed for determining the interval of coda wave from received signals. Results indicate that the start moment of coda wave should be determined as the time corresponding to decorrelation coefficient exceed to 0.2 and the duration is 2.5 ms. Air-coupled LDR scanning experiments were conducted on the honeycomb sandwich specimens with different deboning. Experimental results indicate that the proposed technique is effective for NDT of the debonding in honeycomb sandwich structures. The research provides an efficiency non-contact ultrasonic NDT method for honeycomb sandwich structure.