Detection of Fiber Fracture in Unidirectional CFRP by Remote Field Eddy-Current Testing

Detection of fiber fracture in unidirectional carbon-fiber-reinforced polymer (CFRP) using the conventional eddy-current method is difficult due to the low electrical conductivity of the material. This article explores the possibility of detecting fiber fracture using the remote field eddy-current method. A remote field eddy-current probe consisting of an excitation coil and a reception coil is designed and optimized. The experimental results show that the signal of scanning the probe over fiber fracture has a dual-valley characteristic and the distance between the two minima is identical to the distance between the coil axes. This characteristic of signal is analyzed by studying distributions of eddy current (EC) using a finite-element analysis. A comparison of the testing results of the remote field EC probe and the conventional EC probes demonstrates the superiority of the remote field EC method in detecting fiber fracture in unidirectional carbon-fiber-reinforced polymer.