Characteristics of Eddy Current Distribution in Carbon Fiber Reinforced Polymer

Abstract

The paper studies the characteristics of eddy current (EC) distribution in carbon fiber reinforced polymer (CFRP) laminates so as to guide the research and operation of eddy current testing of CFRP. To this end, an electromagnetic field computation model of EC response to CFRP based on the finite element method is developed. Quantitative analysis of EC distribution in plies of unidirectional CFRP reveals that EC changes slowly along the fiber direction due to the strong electrical anisotropy of the material. Variation of EC in plies of multidirectional CFRP is fast in both directions. The attenuation of EC in the normal direction in unidirectional CFRP is faster than that in isotropic material due to faster diffusion of EC. In multidirectional CFRP, EC increases near the interfaces of plies having different fiber orientations. The simulation results are beneficial to optimizing sensor design and testing parameters, as well as damage detection and evaluation.

A Fuzzy Similarity-Based Approach to Classify Numerically Simulated and Experimentally Detected Carbon Fiber-Reinforced Polymer Plate Defects

“…In other words, even the slightest inhomogeneity of a material can be detected through the test coil, whether geometric, electrical or magnetic variations determine it [20]. Therefore, by adapting the method to each specific case, checks can be carried out to detect inhomogeneities associated with the geometry of the material, such as cracks, deformations, inclusions, thickness variations, oxidations, thicknesses of non-conductive coatings on a conductive basis or of conductive coatings based on different conductivity and variations associated with the permeability of the material by measuring the intensity of the magnetic fields [21][22][23]. Because of the anisotropic behavior of the CFRPs' conductivity due to the delaminations, the conventional NDT techniques fail to quickly detect defects when applied to these composites [24,25].…”

A Study on the Heat and Stress Evaluation of Reinforced Concrete through High-Frequency Induction Heating System Using Finite Element Techniques

“…High-frequency eddy current testing (HF-ECT) techniques that operate at frequencies up to 100 MHz have been reported to be more suitable for this low conductivity material [42,43]. To calculate the skin depth of anisotropic CFRP, Todoroki et al [44] proposed an equivalent analytical model in which the maximum conductivity value along the fibre direction was selected as the apparent conductivity for estimation; however, this method does not consider the effect of anisotropy on eddy current attenuation and skin depth [45]. According to the authors of [46], the effect of conductivity anisotropy on the attenuation of eddy currents is much greater than expected; especially in unidirectional CFR polarities, we observed this phenomenon as the penetration depth of eddy currents decreases rapidly with increasing anisotropic ratios in CFRP complexes.…”