Detection of delamination defects inside carbon fiber reinforced plastic laminates by measuring eddy-current loss

Abstract Carbon fiber reinforced plastics are likely to experience delamination due to the heterogeneity and anisotropy of the materials. However, the through-thickness conductivity of CFRPs is low, resulting in a weak output signal and large amounts of noise interference of eddy current testing in the detection of delamination. Based on the eddy-current loss theory, a method is proposed to detect delamination inside CFRPs. The method consists of an absolute probe with an 8-shaped coil and a unique signal extraction technique using eddy-current loss. The 8-shaped coil of the proposed probe enables the probe to generate a sufficiently strong vertical eddy-current component at its geometric center. The eddy-current loss on CFRPs is extracted by the parallel inductor-capacitor resonance circuit and micro-power detection module. The experiments show that the sensitivity of the vertical 8-shaped probe to the delamination detection is higher than that of the circular and square probes. Compared with ECT, the proposed method by measuring eddy-current loss for delamination has a lower frequency and less noise. In addition, this paper further explores the application of the proposed method in automatic defect detection. The results show that the proposed method can be effectively applied to the automatic detection and visualization of delamination inside CFRPs.