Performance of Hilbert-Curve Based Microwave Sensor for Non-Destructive Testing of CFRP

In this paper a novel Hilbert curve (HC)-based microwave Non-Destructive testing (NDT) array sensor is presented for Carbon fiber based reinforced polymer (CFRP). The suggested sensor was designed on Rogers RT5880 substrate by making use of a combination of third order Hilbert-curve as a resonator. The Transmission coefficient response S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf> and EField distribution are investigated to analyze the performance of proposed sensor. The designed sensor works as bandpass filter in the absence of cracks and as bandstop filter in the presence of cracks across the sensing band of the Sample Under Test (SUT). The fringing field sensing capacitor (FFSC) is used as a “sensing pad” by the HC-based unit sensor, which communicates directly with the SUT to identify surface fractures. The developed sensor operates in the frequency range of 0.25 to 2.75 GHz and can detect cracks as small as 0.5 mm. The developed sensors could be used to increase the safety and integrity of important infrastructure, such as bridges, pipelines, and airplanes, by identifying surface cracks.