Radar absorbing sandwich construction composed of CNT, PMI foam and carbon/epoxy composite

RAS (radar absorbing structure) is effective for both load bearing and EM (electromagnetic) wave absorbing capability of the stealth technology. Although the RAS is usually designed to absorb the EM waves in broadband range of wave frequencies, it may be more effective to absorb the EM waves in certain frequency range as a narrow band stop filter for the specific applications. In this work, non-reflective conditions for the RAS were analytically investigated to determine the medium thickness of EM wave transmission for the destructive interference. Then, the sandwich-type RAS which was composed of CNT (carbon nanotube) nano-composite face, PMI (polymethacrylimide) foam core and carbon/epoxy composite reflector, was fabricated. The EM wave absorbing characteristics of the RAS were measured with the free space measurement method to develop high EM wave absorption characteristics. The flexural stiffness and strengths of the RAS were measured by the three-point bending method with respect to the thickness of the carbon/epoxy composite reflector.