[1C4] Influence of ply orientation on eddy current behaviour in CFRPs using inductive coupling
A Sharma¹, R Hughes¹ and A Peyton²
¹University of Bristol, UK
²University of Manchester, UK
Eddy current testing (ECT) offers a promising approach for non-destructive inspection of carbon fibre-reinforced polymers (CFRPs), enabled by the electrical conductivity of the carbon fibres. However, due to the low and anisotropic bulk electrical conductivity of the CFRP, a complete understanding of how eddy currents flow in these materials is missing, preventing accurate inversion and characterisation of parts. This study investigates how magnetic field attenuation varies with changes in relative ply orientation between CFRP lamina, using a transmit-receive inductive measurement system. Starting with two unidirectional plies, the relative angle between plies is systematically altered to examine the influence of relative ply orientation on eddy current behaviour. Eddy current density is deduced by changes in the magnetic flux measured by the receiver coil as a function of excitation frequency. Finite element modelling (FEM) findings suggest that CFRP samples with a (0°/90°) ply orientation exhibit stronger magnetic field shielding compared to (0°/0°) samples, while at certain other frequencies both orientations shield similarly. Meanwhile, preliminary experimental results suggest that orthogonal orientations do not produce the greatest shielding. These results suggest that frequency, stacking sequence and symmetry significantly impact magnetic field penetration in ways not yet fully understood. This knowledge is crucial for improving ECT simulation models, sensor designs and quality control of CFRP composites, enhancing their structural performance in engineering applications.
