Contactless Eddy Current Sensing for Carbon Fiber Reinforced Polymer Defect Detection


Carbon fiber reinforced polymer (CFRP) is a high performance material that is both mechanically strong and light weight. It has seen wide applications in aerospace and civil engineering, and is being used in high-end consumer products. The composite material is composed of a polymer resin reinforced by carbon fibers. One drawback of CFRP is its susceptibility to impact damages, which raises the need for structural health monitoring. The problem has been a subject of active research recently, with many techniques proposed, including resistance method, electric potential sensing, digital image correlation, and thermal imaging [1]. Compared with these methods, eddy current sensing has advantages in contactless, reliable, and low cost [2]. The challenge in applying it to CFRP lies in the unique electric property: the conductivity is anisotropic, with higher value in the fiber direction (on order of 104 S/m, much smaller than noble metals), and much lower value in other directions (on order of 100 S/m). Therefore, the feasibility of eddy current sensing has to be investigated for CFRP defect detection