Design and Performance Study of Strain Sensors Based on Flexible Frequency- Selective Surface

To address the problem of strain detection in metallic materials, conventional non-metallic substrate flexible frequency selective surface (FSS) strain sensors are susceptible to frequency distortion caused by the interference of the metal under test when measuring on metallic surfaces. Therefore, this study proposes a three-layer flexible FSS sensor with a metal substrate based on the skin effect. By introducing a bottom metal layer, electromagnetic reflection interference from external metals can be effectively isolated, solving the problem of resonant frequency distortion. In order to verify its applicability on metallic curved surfaces, a simulation of metallic cylinder attachment was designed, and the results showed that the sensitivity was 122.78 GHz/% when the pressure inside the cylinder was increased from 0.1 GPa to 0.5 GPa. The results of the tensile experiments show that the frequency of the sensor is shifted from 33.91 GHz to 35.87 GHz with a sensitivity of 1.036 GHz/mm at 0.5-2.5 mm tensile displacement. The design provides a new idea for strain detection in metal structures and expands the potential of FSS sensors in complex engineering environments.