Design, development and application of a novel microwave nondestructive evaluation sensor based on metamaterial lens

Nondestructive Evaluation (NDE) method is one of the primary tools of inspecting different materials for structural reliability. Microwave NDE techniques attract more and more attention from the industry and academia. Microwave NDE techniques have the potential to penetrate deeper into materials such as composites and other dielectrics as compared to ultrasonic techniques. Microwave NDE sensors typically operate in two modes---far field and near field. Although in the far field the standoff distance from the sample is comfortable to a user, the resolution of such sensor is limited by the diffraction limit.;This thesis describes design, fabrication and evaluation of a novel microwave NDE sensor based on a metamaterial lens. It was a purpose of this work to design a novel Microwave NDE sensor based on a metamaterial lens. The proposed sensor would combine a comfortable standoff distance from the sample with a subwavelength resolution. It was shown that in the resonant frequency range of 3--4 GHz the designed lenses can focus below the diffraction limit (0.48 lambda) and that defects as small as 0.037 lambda in diameter in a dielectric sample can be detected. The resolution was further improved by introducing a metamaterial lens with resonant frequency of 16.75 GHz. Applicability of the proposed sensor to other samples such as corrosion spot under space shuttle tile and rippling on the surface of carbon fiber composites was shown. The limitations of the method were also discussed.;The proposed sensor is a viable alternative to the existing NDE methods and contributes greatly to advances in the field of non destructive evaluation.