Enhancement of sensitivity to delamination in eddy current testing of carbon fiber composites by varying probe geometry

An eddy current testing method is proposed to improve the sensitivity to delamination in carbon fiber reinforced plastics (CFRPs). The distributions of the eddy current density and magnetic field are investigated using finite element method analyses to identify the effect of delamination on the electromagnetic field. The change of the magnetic field induced by delamination is calculated and it is found that a distinct improvement of the sensitivity to delamination can be achieved by optimizing the distance between the tangential driver and pickup coils. Experiments performed for cross-ply CFRP samples verify that the sensitivity of the eddy current sensor can be improved such that the signal change caused by delamination is not masked by the signal changes caused by the electrical conductivity variation in CFRP. Embedded delamination with a length and width of 10 mm are clearly visualized using the proposed eddy current method.