Synthesis and electromagnetic characterization of frequency selective radar absorbing materials using carbon nanopowders

A new method for the synthesis of multilayered radar absorbing materials is analyzed by using carbon nanomaterials. With respect to the literature, a desired profile of reflection coefficient is a priori established as a function of the frequency. The goal of the synthesis is to follow this target profile by computing thickness and type of the material of each layer until the reflection coefficient of the electromagnetic-wave absorber best approximates the wanted reflection coefficient. The material available for each layer is epoxy-resin reinforced by different kind of carbon-based nano/micro powders: graphene nanoplatelets, carbon nanofibers, multi-walled carbon nanotubes and polyaniline. The dielectric characterization of the composite materials is performed in the frequency range 2÷18 GHz. The synthesis uses evolutionary computation by drawing on the electric permittivity of composite materials. Three square layered electromagnetic wave absorbers of 25 cm side are manufactured. The comparison between the target, the simulated and the measured reflection coefficients shows a good agreement thus confirming the scientific validity of the dielectric characterization and the proposed design method. Finally, a finite element analysis has been carried out to explain the mechanism of electromagnetic wave absorption by a multilayer and to simulate a low radar observable naval military gun.