Stealth technology is important for weapon systems to increase their survival in operation because the stealth technology makes them less visible to the enemies by reducing the RCS (radar cross section). The RAS (radar absorbing structure) is the most effective method for performing both the load bearing and EM (electromagnetic) wave absorbing abilities.
The RAS is usually designed to absorb EM waves in broadband range of EM wave frequencies. However, it could be more effective to absorb EM waves in certain frequency range as a narrow band stop filter for specific case such as applying the low-observable radome because the low-observable radome is only allowing the pass through of the in-band EM wave with narrow band frequency.
In this work, the nonreflective conditions of the RAS were analytically investigated to determine the medium thickness which was related to the EM wave wavelength for resonant conditions. Then, the frequency selective RAS composed of CNT nanocompoiste face, PMI foam core and carbon/epoxy composite was fabricated. Also, the EM wave transmission characteristics of the RAS were numerically simulated with the 3-dimensional EM wave analysis software, CST Microwave Studio (CST Gmbh, Germany) and measured with the free space measurement system (HVS Technologies, Pennsylvania, USA). The mechanical performances of the RAS were measured by the 3-point bending test and the optimum thickness of carbon/epoxy composite was determined for the reflector of the RAS with repect to the specific flexural strength.