Design of electromagnetic wave absorbing sandwich composite for secondary bonding application

In this study, a novel electromagnetic (EM) wave absorbing composite sandwich structure and its application process are proposed. The composite sandwich can be applied to the outer part of structures as a final surface treatment through a secondary bonding process, and this covers all the surface components that illuminate the incident EM waves. This process improves the structural material properties of the original components and their durability against the environment in contrast to EM wave absorbing paint or patch. With the help of EM wave absorbing characteristics and continuous impedance of the composite sandwich structures, the EM signals from reflection, diffraction, and scatter decrease effectively. The outer skin of the composite sandwich includes a resistive periodic patterned sheet prepared using printed electronics, and a low-dielectric foam is adopted as the core material. This composite is designed based on the equivalent circuit theory and is subsequently fabricated. The EM characteristics are tested after application on an aircraft skin structure through a secondary bonding process. The measurement of reflection loss and image processing of the reflected signal show that this composite and application process decrease the EM wave reflections from the original structure significantly.