Broadband all fiber-reinforced composite radar absorbing structure integrated by inductive frequency selective carbon fiber fabric and carbon-nanotube-loaded glass fabrics

A broadband radar absorbing structure (RAS) covering both X and Ku bands (8.2–18.0 GHz) was designed by integrating an inductive frequency-selective carbon fiber fabric composite (FSFC) and multiwalled carbon nanotube (MWCNT)-loaded glass fabrics which can modulate EMI characteristics of the FSFC. All the layers of the structure consisted of fiber-reinforced fabrics, and thus general composite fabrication processes can be easily applied. An existing scaling law based on the percolation theory was modified to replicate permittivity of the MWCNT-loaded fabrics. Coefficients and exponents of the power law were expressed by frequency and MWCNT concentration. The modified model provides a good description of the dielectric property of MWCNT fabric composites, and thus paves the way for parametric evaluation of reflection loss of the FSFC-embedded double-layered RAS regarding the permittivity of the lossy dielectric composites, as well as thickness of each layer and the total thickness of the RAS. The reflection loss of the RAS, drawn from the parametric study, can cover 10 dB in the whole X and Ku bands with two separated absorption peaks, while its thickness was 3.63 mm only.