Experimental Research of Eddy Current Testing Technology Based on Resonant Circuit in Carbon Fiber Reinforced Polymer Testing

Abstract

When implementing eddy current testing for carbon fiber reinforced polymer (CFRP), it is usually necessary to apply a higher testing frequency and analyze the voltage amplitude and phase changes of the output signal of the testing coil to identify defects. In this paper, a three-point capacitive resonance circuit is designed to identify artificial defects of carbon fiber reinforced polymer by detecting changes in the frequency of the output signal. The research in this paper has the following conclusions: 1. Through the change of resonant frequency, artificial defects with groove width of 0.50mm, groove depth of 0.50mm, 1.00mm, and 1.50mm can be effectively identified; 2. When the lift-off distance is less than 1.00mm, the resonance frequency does not change much; 3. Compared with the traditional analysis of voltage amplitude and phase changes to identify defects, the resonance frequency method can use a data acquisition card with a lower sampling frequency to realize the identification of the signal frequency (defect); 4. The detection sensitivity of the disc coil is higher than that of the rectangular coil; 5. The greater the inductance of the disc coil, the higher the resonance frequency and the higher the detection sensitivity.