Design and comparison of directional transmit to differential receiver eddy-current probe for in-line monitoring of automated fibre placement


Mussatayev M. Yi Q. Wilcox P.D. Hughes R.R.
15 November 2025Elsevier Ltd

Composites Part B: Engineering
2025#307

Automated fibre placement (AFP) manufacturing systems help to increase the production rates of Carbon Fibre Reinforced Polymers (CFRP), however, the in-line inspection of AFP remains a challenge for the Non-Destructive Evaluation field. This paper reports on a directional eddy-current testing (ECT) probe developed and tested for in-line detection of common AFP composite prepreg defects such as in-plane waviness and out-of-plane wrinkles. A directional transmit and differential receiver sensor previously developed for detection of out-of-plane wrinkling in cured carbon fibre composites was evaluated and adapted for the detection of in-plane waviness in un-cured CFRP. A figure-8-shaped transmitter coil is employed to increase current density along the fibre direction. Differential receiver coil designs with different aspect ratios were evaluated over a range of suitable frequencies to optimise the probes for sensitivity to in-plane fibre waviness. An advanced finite element modelling approach was employed to simulate the probes above CFRP tapes containing waviness and the results compared to experimental findings. The results demonstrate that a design using square differential receiver coils is most sensitive to in-plane wrinkling, while a lift-off study revealed that the ECT probe can be operated up to 0.3 mm from the material surface while maintaining effective detection of fibre waviness.

Automated fibre placement , Eddy current testing , Non-destructive evaluation , Probe optimisation , Uncured composite

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School of Electrical, Electronic and Mechanical Engineering, University of Bristol, Bristol, BS8 1TR, United Kingdom
Kazakhstan Institute of Non-Destructive Evaluation LLP, Flat 367, 43 Saryarka Avenue, Astana, Z10H9C3, Kazakhstan
Department of Aviation Technique and Technologies, Civil Aviation Academy, 44, Zakarpatskaya Str, Almaty, 050039, Kazakhstan
Department of Computer and Information Sciences, Northumbria University, United Kingdom

School of Electrical
Kazakhstan Institute of Non-Destructive Evaluation LLP
Department of Aviation Technique and Technologies
Department of Computer and Information Sciences

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