Linear Excitation Eddy Current Probe for Multi-layered CFRP Inspection

Rosell, Anders; Michigan State University; United States

Rosell, A.; Michigan State University; USA
Ye, C.; ShanghaiTech University; China
Deng, Y.; Michigan State University; USA
Udpa, L.; Michigan State University; USA
Upda, S.; Michigan State University; USA

ID: ECNDT-0269-2018
Download: PDF
Session: Eddy Current-Techniques 2
Room: H2
Date: 2018-06-14
Time: 13:50 - 14:10

Carbon fiber reinforced polymer (CFRP) composite is widely used because of its excellent material properties. However, damages may occur during the manufacturing and service of CFRP and degrade the material eventually leading to failure of components and structures. The traditional non-destructive evaluation (NDE) techniques, using ultrasonic or X-ray, have faced difficulties in detection of damage in CFRP, and it is important to study new NDE methods. Electromagnetic NDE based on eddy current principles works excellent for evaluation of the conductive fiber structure of CFRP. Induced currents flow easily within carbon fibers and any damage or anomaly that influence these currents might be detected. To take advantage of the high conductivity along fibers, we propose a linear excitation eddy current probe that can change the orientation of excitation current electrically. Since the electrical conductivity of CFRP is anisotropic, eddy currents are more effectively induced by a linear coil excitation source compared to a circular coil. The orientation of defects as well as fiber structure can be characterized by electrically changing the orientation of the linear current excitation, making this approach more versatile and sensitive. The operation of the probe is shown using a simplified finite element model. A prototype sensor is built and compared to a conventional coil for simple shaped defects in CFRP sample. We also show how defect orientation and fiber structure can be evaluated by using the linear current excitation probe and compare it to circular current excitation using a coil.