Electromagnetic property of a novel gradient honeycomb composite fabricated by 3D forming

In order to get the wide band absorbing and shielding composite, a novel gradient honeycomb absorber was designed as the polyethylene terephthalate glycol (PETG) was matrix and carbonyl iron particles (CIPs) and flaky Cu were the absorbents. The composite was fabricated by 3D printing and the morphology was obtained by the scanning electron microscopy. The permittivity and permeability of the absorbing wire were tested with the vector network analyzer. Using the transmission and reflection method, the parameters of the columnar and gradient honeycomb elements were simulated. The equivalent parameters were calculated based on the Maxwell-Garnett mixing rule, then the simulated and calculated results including reflection loss (RL) and shielding effectiveness (SE) were compared, the mixing rule was effective to calculate the equivalent parameters and the shape factor was the key parameter. Using the interpolate method on the shape factor, the permittivity and permeability of honeycomb with random size could be calculated. Finally, RL and SE were optimized using the genetic algorithm in which the structure lengths were the variables. The result indicated that the structural composites had an excellent absorbing property (minimum RL −28 dB) in 8–12 GHz and SE was larger than 20 dB. As the incident wave was oblique, the absorbing property was also excellent (minimum RL −35 dB@35°), the angle range was 0–70° with RL less than −10 dB. It could be implied that the novel gradient honeycomb was a potential good absorbing structure.