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.
Highlights
Honeycomb sandwich composite materials have been widely used in aerospace and aviation industries owing to their excellent physical and mechanical properties, such as high specific strength, high specific stiffness, good sound, and heat insulation property [1,2,3]
The ultrasonic propagation in aluminum, glass fiber reinforce polymers (GFRP), epoxy resin adhesive layer can be attributed to stress-strain problem in solid field
This indicates that the transmission longitudinal wave T1 has a good response to the debonding defect, that is to say, it can effectively characterize the debonding defect based on the transmission longitudinal wave T1
Summary
Honeycomb sandwich composite materials have been widely used in aerospace and aviation industries owing to their excellent physical and mechanical properties, such as high specific strength, high specific stiffness, good sound, and heat insulation property [1,2,3]. Owing to the influence of temperature, pressure, and other factors, honeycomb composite materials often suffer from delamination defects, debond defects, or inclusion defects in the manufacturing and service process [4,5]. Using effective methods [19,20,21] to overcome these limiting factors is the key to applying the air-coupled ultrasonic testing technique to the quality inspection of honeycomb sandwich composite materials. The application of air-coupled ultrasonic technology to the non-destructive testing of debonding defects of honeycomb sandwich composites is studied and demonstrated. Based on the air-coupled pulse compression signal, the C-scan of honeycomb sandwich composite with embedded debonding defect is carried out, and the accuracy and effectiveness of air-coupled ultrasonic testing technology are verified
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