Non-destructive testing of carbon-fiber-reinforced plastics with a PCB-based T-R probe

Abstract

Circular coils are widely used in non-destructive testing of traditional isotropic materials. However, from the perspective of anisotropy and low conductivity of carbon-fiber-reinforced plastics (CFRPs), square coils which can effectively improve the electromagnetic coupling between carbon fibers and coil wires, are more suitable for CFRPs. Concerning this issue, a method using PCB-based transmitter–receiver (T-R) probe with square spiral coils for non-destructive testing of CFRPs was proposed in this paper. The proposed probe consists two square spiral coils manufactured on printed circuit board. Rotation experiments on unidirectional laminates, orthogonal woven laminates, four-directional angle-ply laminates were carried out. Results show that the characterization of fiber orientations can be realized. Scanning experiments show that the proposed method can be used to detect cracks, in-plane waviness and abnormal fiber distribution. The length of cracks can be estimated from the scanning images. By comparison of scanning image obtained along different fiber orientations, anisotropic of CFRPs can be reflected. It also shows that the proposed method can selectively detect defects in specific direction.