Non-contact characterisation of Carbon Fibre Reinforced Plastics in hybrid aluminium / CFRP sheets using multi-frequency eddy current sensors

The characterization of hybrid aluminium / Carbon Fiber Reinforced Plastics (CFRP) sheets using multi-frequency eddy current sensors is presented in this paper. Both air-cored circular sensors and highly directional ferrite-cored sensors are designed for bulk conductivity measurements and directionality characterization. An analytical model describing the interaction of the circular sensors with the hybrid planar structure is developed. Finite element (FE) models that take into account of the anisotropicity of the CFRP have also been proposed. Both models are in good agreements with experimental results. The features of the sensor output signals are analyzed and explained. It is believed this is the first published report of using eddy current techniques for characterizing the hybrid aluminium / CFRP material.