Thin Film Coating of Glass Fabrics for Radar Absorbing Composites

Abstract

By the invention of radio and micro wave range in electromagnetic spectrum, some radar systems were started to use to predict the range, altitude, direction or speed of objects. During the Second World War, the scenario changed significantly and this led to the development of the radar absorbing materials (RAM’s). Then the stealth technology and Radar Cross Section (RCS) terminologies took place in science research area. To reduce of an objects detectability in the radar detection systems, the reduction of the radar cross section play an important role. For absorbing electromagnetic micro waves, radar absorbing materials have been developed and they consist dielectric and magnetic materials that has capacity for absorbing. In order to increase frequency range (bandwidth) of the absorbance, several materials have been already proposed by several researchers. But nowadays, studies on investigating the radar absorbing structures (RAS) using fiber reinforced polymeric composite materials, are becoming popular research field. The purpose of this study is to design, fabricate and characterize RAS’s based on unidirectional E-glass fiber reinforced epoxy resin composites which can absorb microwave within 2-20 GHz frequency range. Several Jaumann design composite structures were manufactured to achieve radar wave absorbance. In this Jaumann structures, we use different designs in terms of different resistive values of sheets and different thickness of composites. In addition to this, we also focused on the different concentration of additives and distance between resistive sheets. Glass fiber / epoxy system were employed as a base structure. Carbonyl Iron powders were used to change permittivity, permeability and intrinsic impedance values of the structure. To functionalize the glass fibers and to make them conductive, surface of them was metalized by using large area planar magnetron sputtering system. These conducting layers act as a resistive sheet within the composite structure. Surface resistances of resistive sheets used in structures show diversity between ≈ 430 ohms and to 30 ohms.