Detection and Characterization of Debonding Defects in Aeronautical Honeycomb Sandwich Composites Using Noncontact Air-Coupled Ultrasonic Testing Technique

Abstract

The finite models of honeycomb sandwich composite with intact and embedded debonding defects are constructed. The sound pressure in fluid domain and the stress strain problem in solid domain are related by acoustic-structure coupling method, which visually shows the propagation process and modal characteristics of the acoustic wave inside the honeycomb sandwich composite. The simulation results show that the transmission longitudinal wave T1 (transmission initial wave) can effectively characterize debonding defects of honeycomb sandwich composite. However, in the actual detection of honeycomb sandwich composite, there are some problems, such as poor Signal-to-noise ratio (SNR) of received signal, incognizable transmission initial wave. In order to solve these problems, this paper proposes to apply polyphase coded pulse compression technique to air-coupled ultrasonic testing system. The actual test results show that the SNR of received signal is effectively improved, the transmission initial wave can be effectively identified, and the compressed signal has a good response to debonding defect. The air-coupled ultrasonic testing C scan result of honeycomb sandwich composite verifies the rationality and correctness of the theoretical simulation and signal processing technique, which promotes industrial application of air-coupled ultrasonic testing technique in the aerospace field.