Method of Defects Detection in Non-Metallic Composites Based on Liquid Flow Controlled Spoof Surface Plasmon Polaritons

This paper proposes a new microwave non-destructive testing (NDT) method based on liquid flow controlled spoof surface plasmon polaritons (SSPPs) to detect defects in non-metallic composites. The sensor based on this method is composed of SSPPs structure and liquid flow controller. The liquid flow controller can be used to control the sensing area of the sensor. The detection is based on the change of the transmission coefficient at the cut-off frequency of SSPPs sensor, which is caused by defects. Since liquid movement has continuity, the sensor's field distribution is also continuous change. So in a certain detection range, the liquid flow scanning method can avoid the problem of defect missing detection. Taking FR4 as an example, both the simulation and experiment results reveal that this liquid flow controlled SSPPs sensor can effectively realize defects detection with a radius of 1mm in non-metallic composites. The sensor has the advantages of simple structure, easy operation, fast detection speed and convenient detection of curved MUT.