It is such an important issue not only for military purposes but also from commercial point of view that whether the reflective wave from an incident electromagnetic wave can be nullified. In this research, by blending conductive carbon black with the binder matrix of glass/epoxy composite, a Radar Absorbing Structure (RAS) which can support loads and absorb the electromagnetic wave was designed. The RAS was specially designed to exhibit the optimum absorptivity for X-band (8.2-12 GHz) of frequency ranges, centered at 10 GHz.
The dielectric and mechanical properties of specimens with different weight percentage of carbon black were measured. The optimum blend of carbon black weight percent was identified for the absorption of X-band radar frequency by specifying the corresponding thickness using the absorbing bandwidth map with respect to thickness and frequency.
By the combination of two blends of multi-layered RAS it was proved that the comparable performance could be achieved to the single-layered RAS. Considering its mechanical properties, the most optimum RAS can be produced using CB7 (7wt%) layer and CB5 (5wt%) layer blends. The layers were arranged in the following manner; the first layer of CB7 (thickness 0.6 mm) and second layer of CB5 (thickness 1.9mm), and the reflection loss was measured by using maximum RCS measurement technique of plates. Unlike other existing measurements of reflection loss using a waveguide, the reflection loss within an anechoic chamber simulating RCS (Radar Cross Section) method of measurement was used with plane-wave shaped incident wave. The optimum structure showed 2.4 GHz in 10 dB absorbing bandwidth and 0.64 GHz in 20 dB absorbing bandwidth within the X-band frequency range.
