Numerical Investigation of the Impact of a Conductive Defect Submerged in a Carbon Fiber Reinforced Polymer Plate with Circular Multi-Coils Eddy Current Sensor

During eddy current testing, most defects observed in conductive materials are generally interpreted as loss of material. However, there are other types of defects that initially appear as material loss, but can later be filled with polluting substances. These polluted conductive substances will entirely or partially fill the volume of the primary defect. It is therefore essential to take this type of defect into the modeling by representing them as electrically conductive volumes. These defects include impurities, inclusions and micro-welds ... etc. For this study, the focus lies on investigating a rectangular shaped defect aligned with the direction of the fibers. The defect occupies 25 to 200% respectively of the total longitudinal conductivity of a four-ply CFRP plate. To achieve this, a circular multi-coils sensor was developed. We investigated electromagnetic phenomena using a three-dimensional (A) over right arrow - v formulation, and then we resolved this later using a numerical approach called the finite element method. The cartography of the induced currents densities in the presence of the defect are depicted and the simulation results obtained from the normalized impedance are plotted in the polar diagram. This investigation demonstrates through numerical simulation that this type of defect must be taken into consideration in order to complete the developed models.