ECT in composite materials using double excitation coils and resonant excitation/sensing circuits

•Comparison of two ECT probes in a CFRP material using FEM.•Probe implementation with double excitation coils for defect detection in CFRP.•Application of resonance frequency in probe circuits enhance defect detection. Carbon Fiber Reinforced Plastic (CFRP) materials are becoming more and more important for several engineering applications because of its combination of high strength and low weight. CFRP is an anisotropic material with low conductivity that usually requires eddy current testing (ECT) probes operating at high testing frequencies to inspect these materials. The detection of defects is highly dependent on the sensitivity of the probes and their performance to minimize the effect of noise existing during the real inspection. In this study, an ECT probe was developed for crack detection in CFRP materials. Simulation studies demonstrate that the proposed probe design can be more sensitive than the two coil transmit-receive probe. The comparison was done in terms of magnitude of the voltage induced in the sensing coil for the same conditions of test. In the experimental study, resonance frequency techniques in the excitation and sensing circuit were included to improve the sensitivity of the proposed probe. The results clearly show the detection of small cracks and fiber “tissue” in the scanned images.