Radio & Electromagentic Absorbent Materials

 

Further to my thoughts on using a Faraday Cage as part of the structure, the use of radar absorbing materials would improve the security of the structure and offer a wide variety of design options.

Radar absorbing materials and structures are designed to absorb radar waves and convert them to heat. Because these radar waves are not returned, radar absorbing materials (RAM) and radar absorbing structures (RAS) provide a reduced signature for detection. Typically, RAM and RAS are used in defense applications and in commercial communications activities that require the absorption of electromagnetic interference (EMI) and radio frequency interference (RFI).

Materials & Structures

Radar absorbing materials and structures include iron ball paint, foam absorbers, and Jaumann absorbers. Iron ball paint consists of tiny iron particles that are coated with carbonyl iron or ferrite. These particles are similar to the ferrite grains and carbon black particles embedded in the neoprene polymer sheets used in some military applications. Foam absorbers also use carbon black, but in urethane foam. Pyramidal RAM is achieved via scattering and absorption. Jaumann absorbers or Jaumann layers are radar absorbing materials and structures that use wave-interfering techniques to cancel the reflected waves.

Uses

Radar absorbing materials and structures are probably best-know for their use in stealth technology, such as on the surfaces of the U.S. Air Force’s F-117 Nighthawk. In addition to their use on stealth bombers, however, RAS and RAM are used in commercial microwave communications applications. Examples include antennas, car radios, mobile phones, and telecommunications base stations

STEALTH BOMBER

HONEYCOMB

A lightweight core material that is constructed with hexagonal cells. It can tuned to operate at various frequencies over a broad spectrum. The electrical performance can be maximized for insertion / transmission or reflection loss.

  • Designed to enhance antenna performance
  • Ultra lightweight yet mechanically durable
  • Superior electrical performance
  • Machined to complex 3D configurations

Honeycomb structures can offer maximized performance from low to high frequencies, with the construction, configuration and cell structure it can also offer outstanding reflection, insertion / transmission loss.

 

Carbon Nanotubes

Carbon nanotubes are used as conductive fillers in epoxy resins and to replace ferrites based fillers classically used in radar absorbent materials. Ferrites provide good absorption properties but present several drawbacks like: high density, sensibility toward corrosion.

Carbon nanotubes and polyaniline which is an electrically conducting polymer. which both have low density and good absorption properties. By combining  carbon nanotubes with polyaniline it dramatically enhances the EMI shielding properties of composites thanks to a synergistic effect.

carbon nanotube

 

 

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