Structural Health Monitoring of Aerospace Structures using Guided Electromagnetic Waves in a Dielectric Waveguide at Ka-Band

Dielectric waveguide (DW) antenna systems are widely used in millimeter-wave radar applications. A large and innovative field is Structural Health Monitoring (SHM) of aerospace structures. The proposed research aims at detecting structural changes and potential defects at Ka-band on metallic structures that represents the device under test (DUT). To determine the severity of damage compared to the pristine structural state, dimensionless damage indicators (DI) are calculated by the root-mean-square deviation (RMSD) and correlation coefficient deviation (CCD) methods. The geometric design of the DW is crucial for a barrier-free propagation of guided electromagnetic waves (EWs) of a specific frequency bandwidth inside the dielectric material. In the presented approach, a rectangular DW is designed through numerical modelling which contains a polypropylene (PP) matrix, aluminum walls and two K-connectors, each with an inserted pin. The DW is attached to the surface of a nearly plane DUT connected externally to a vector network analyzer (VNA) that measures the elements of the scattering matrix (S-parameters). The reflection and transmission behavior, reflected in the S-parameters, provide information about the interaction of guided EWs with a damage. It was found that damage sizes of 2 mm can be detected reliably with the proposed methodology. The full paper will present and discuss numerical simulations with CST Microwave Studio with a comparison to experimental measurements.