Design and fabrication of radar absorbing structures including frequency selective fabric composites

Abstract

In this study, the double-layered radar absorbing structure (RAS) including a frequency selective fabric composiate (FSFC) with broadband absorption over a wide frequency range was developed based on the understanding of the following concepts; the mechanism of the induction of the permittivity into the matrix system and the fiber-reinforced composites, EM characteristics of the multi-layered RAS, the FSFC, and the RAS including a FSFC, and the problems occurring in the fabrication of the layer-stacked structure. Compared to established radar absorbing materials (RAM), the RAS consisting of fiber-reinforced composites is expected to carry loads and also absorb electromagnetic (EM) waves. First, MWNT/epoxy nanocomposites were fabricated to investigate the possibility of using MWNT as a loss filler for induction of dielectric losses and as a reinforcement for improvement of mechanical properties. Second, MWNT-added plain-weave glass/epoxy composites were fabriccated as a material of RAS. The dielectric and mechanical properties of the composites were investigated with respect to MWNT loadings, microstructures, and glass fiber volume fractions. From the investigation, up to a critical loading of MWNT, the materials were fabricated for use as a RAS material, whose dielectric losses increased and mechanical properties also were increased or maintained same in comparison to the composite containing no filler. A RAS fabrication process was proposed, because the plain-weave glass/epoxy composites had the nonlinearty of the thickness per ply with MWNT contents and with the number of plies. The comparison between the theoretical and experimental reflection loss revealed that the process was successfully applicable to the fabrication of multi-layered RASs. The FSFC, as a novel inductive FSS, was proposed consisting of carbon and low-loss dielectric fibers. The design parameters and EM characteristics were widely discussed in terms of the anisotropic properties of con...