Evaluation of detectability of differential type probe using directional eddy current for fibre waviness in CFRP

Abstract

This paper describes the detectability of eddy current testing (ECT) using directional eddy current for detection of in-plane fibre waviness in unidirectional carbon fibre reinforced plastic (CFRP) laminate. Three different types of probes, such as circular driving, symmetrical driving and uniform driving probe, were proposed, and the waviness angle was extracted from the contour map of the ECT signal by applying a Canny filter and a Hough transform. By comparing both the waviness angle estimated by ECT and that obtained by an X-ray CT image, the standard deviation (precision) and root mean square error (accuracy) were evaluated to discuss the detectability of these probes. The directional uniform driving probe shows the best detectability and can detect fibre waviness with a waviness angle of more than 2° in unidirectional CFRP. The probe shows a root mean square error of 1.90° and a standard deviation of 4.49° between the actual waviness angle and the angle estimated by ECT. This article is part of the theme issue ‘Advanced electromagnetic non-destructive evaluation and smart monitoring’.

A new probe‐based electromagnetic non‐destructive testing method for carbon fiber‐reinforced polymers utilizing eddy current loss measurements

“…Furthermore, _ U R _ I can be used to characterize the eddy current loss. Equation (15) indicates that the power of the magnetic flux of the primary magnetic field passing through the sensor is 0; therefore, using _ U R _ I to characterize the eddy current loss shields the interference of the primary magnetic field.…”

“…1 Several studies have reported on the inspection of CFRPs based on the ECT method. [14][15][16] The unidirectional layer of CFRP exhibits strong anisotropic conductivity, resulting in extremely low bulk conductivity that is three orders of magnitude smaller than that of other materials. 17 As this weakens the induced eddy current, the detection signal is considerably low.…”

“…As carbon fibers are conductive, structural information such as fiber distribution and texture can be obtained using ECT scans 1 . Several studies have reported on the inspection of CFRPs based on the ECT method 14–16 . The unidirectional layer of CFRP exhibits strong anisotropic conductivity, resulting in extremely low bulk conductivity that is three orders of magnitude smaller than that of other materials 17 .…”

Towards Real-Time Railroad Inspection Using Directional Eddy Current Probe

“…A substantial body of research has been dedicated to the optimization of EC probes, with various studies focusing on enhancing their efficacy in diverse applications. In an exploration of the efficacy of ECT for in-plane fiber waviness detection in unidirectional carbon fiber reinforced plastic (CFRP), [21] employed a diverse set of probes: circular driving, symmetrical driving, and uniform driving. This study is distinguished by its methodical comparative analysis and the integration of sophisticated image processing techniques, including the Canny filter and Hough transform, to ascertain the probes' precision and accuracy against X-ray CT imaging benchmarks.…”

A novel method based on eddy‐current equilibrium for improving the sensitivity of fiber orientation detection

“…[14] Na Zhang and Hiroyuki improved the detection ability of the probe for micro-defects inside CFRPs by utilizing differential probes that can suppress common mode noise and implementing a series of signal processing algorithms. [15,16] Others are committed to enhancing the signal intensity of the receiving coil. For example, Wu et al developed a high-frequency PCB-based TR probe and clearly detected the fiber orientation in unidirectional CFRP plate at frequencies up to 40 MHz.…”