Electromagnetic absorption of sandwich panel made of glass fiber reinforced polymer and nanocomposite foam filled honeycomb

Abstract

Sandwich panels were processed and characterized for electromagnetic absorption. The faces are made of glass fiber reinforced epoxy. The core of the panel is made of carbon nanotubes reinforced polymer foam filling a metallic honeycomb. Electromagnetic modeling and experimental characterization of the core showed that the honeycomb, acting as a hexagonal waveguide, improves the absorption properties in the GHz range above the cut-off frequency compared to the composite foam alone. The EM absorption can be tuned by changing the hybrid material properties. The required levels of electrical conductivity are attained owing to the dispersion of low amounts (1-2wt%) of carbon nanotubes inside the polymer matrix. The combination of the foam and a honeycomb architecture contributes to the decrease of the real part of the relative effective permittivity ℜ( , ). Varying the cell shape of the honeycomb changes the frequency range for high absorption. The absorption properties of sandwich panels has been measured from 8 to 40 GHz and succesfully compared to predictions from an analytical model developed for multilayered topologies. Our results show that a careful design of face-sheets allows to preserve and even improve the absorption performances of the hybrid in a dedicated frequency range.

Design of compact multi-layer microwave absorber for ultra-wide band applications thru shaping and RAM technologies

“…Its cell size of 4.76 mm and material thickness 7 mm give higher RCS values approach −20 dB at lower frequency ranges. Sandwich panels were proposed in [2], where honeycomb faces are made of glass fiber reinforced epoxy and the core is made of carbon nanotubes reinforced polymer foam filling a metallic honeycomb. The proposed honeycomb structure is of 7 mm thick and cell size of 5.5 mm filled with PC-CNT 1 wt% foam.…”

“…Since, the propagation within each honeycomb cell is influenced by its metallic walls in addition to the honeycomb cell dimensions as depicted in figure 2, therefore, EM analytical modelling of the proposed structure is then started by calculating the effective permittivity expression of the honeycomb structure from a classical rectangular waveguide model [2,6]. Assume that the rectangular waveguide sector surrounding each honeycomb hexagon unit cell has shape setting angle ψ = 60 • and side dimensions of a, b with inner hexagon cell size a h − T h .…”

“…Assume that the rectangular waveguide sector surrounding each honeycomb hexagon unit cell has shape setting angle ψ = 60 • and side dimensions of a, b with inner hexagon cell size a h − T h . Where a h and T h are the outer hexagon cell size and the thickness of each hexagonal unit cell (wall thickness) respectively [2]. The transverse electric TE 10 (m = 1 and n = 0) mode will be considered only, then the measured off honeycomb unit cell parameters can be related to rectangular waveguide side dimensions as:…”

“…Also, they increase the immunities of the electronic equipment to work probably in the presence of radio frequency interferences in EM susceptibility (EMS) mode [1]. Unwanted EM radiations have to be cancelled either by reflecting back their incidences thru a shaped metallic surface or by totally absorbing their EM energy through RAM [1,2]. Furthermore, strong attention is considered to methods of decreasing RCS detectability.…”

Electromagnetic Interference Reflectivity of Nanostructured Manganese Ferrite Reinforced Polypyrrole Composites

“…Among the conventional microwave absorption materials, the spinel-type ferrites are popular. However, spinel-type ferrites show Snoek's limit, and the magnetic loss decreases at giga-hertz range [11][12][13][14]. Earlier, spinel ferrites have been most frequently utilized as absorbing materials, in various forms.…”