Design and preparation of an epoxy resin matrix composite structure with broadband wave-absorbing properties

Aiming at the poor effect of broadband wave-absorbing, the structural wave-absorbing composites structure were designed and prepared by choosing FeNi alloy powder/epoxy nanocomposites as the wave-absorbing interlayer, and carbon fibers/epoxy composites as the structural materials. Firstly, “80 wt% Fe50Ni50 alloy powder/epoxy resin nanocomposites” were successfully prepared, with a density of about 2.4 g/cm3, which can be applied as wave-absorbing interlayer. Then, electromagnetic parameters and loss mechanisms of the wave-absorbing sandwich in the frequency band of 1–18 GHz were studied in detail. Finally, the radar wave absorption characteristics of the structural wave-absorbing composites were optimized. The study shows that the electromagnetic loss mechanism of wave-absorbing sandwich is dominated by conductive loss and eddy current loss in the frequency range of 1–6 GHz, and eddy current loss, resonant loss and relaxation polarization in the frequency range of 6–18 GHz. In the frequency band of 2.5–8 GHz, the angular tangent of the magnetic loss of the interlayer is tanδm ≥ 0.5, and, the attenuation constant is stabilized in the range of 160–180 in the frequency band of 5.2–13.2 GHz, which shows that the interlayer has a good capacity of electromagnetic wave absorption. Different wave-absorbing properties can be designed by changing the thickness of the wave-absorbing interlayer. And the “fiberglass/interlayer/carbon fiber” composite board with a thickness of 2.0 mm interlayer and 3.0 mm-thick “fiberglass/ epoxy” has excellent broadband wave-absorbing properties. The sandwich composites have wave-absorbing peaks of |RL|≥10 dB in the frequency bands of 4.93–8.79 GHz and 14.96–18.0 GHz, with the peak width of 6.90 GHz, and the absorption peak of |RL|≥54 dB.