Abstract
Layered carbon fiber composites (CFC) with enhanced shielding effectiveness (SE) were prepared with mixed fillers of carbon nanotubes (CNTs) and carbonyl iron powders (CIPs) in the form of a Koch curve fractal. In the layered composite structure, glass fiber (GF) cloth was used in the wave–transmissive layer (WTL), and the carbon fiber (CF) cloth was used in the supporting layer (SL). Between WTL and SL, CNTs and CIPs were distributed in epoxy resin in the form of a Koch curve fractal to act as an absorbing layer (AL), and copper foil was used as a reflective layer (RL) and bonded at the bottom of the whole composites. The layered structure design and excellent interlayer interface integration obviously improved the SE performance of the CFC. The SE of different samples was investigated, and the results show that, with the increase in the number (n) of Koch curve fractals, the SE of the samples enhanced in the low frequency scope (1–5 GHz). The sample with n = 2 has the highest SE value of 73.8 dB at 2.3 GHz. The shielding performance of the fractal sample filled by CNTs and CIPs simultaneously has a comprehensive improvement in the whole scope of 1–18 GHz, especially for the sample with n = 2. The cumulative bandwidth value of the SE exceeding 55 dB is about 14.3 GHz, accounting for 85% of the whole frequency scope, indicating the composite fabricated in this paper is an electromagnetic shielding material with great prospect.
Highlights
Electromagnetic interference (EMI) shielding materials are widely used in the military, industry, aerospace, and electronics to reduce electromagnetic interference [1]
When an electromagnetic wave irradiated the surface of the composite, the wave–transmissive layer (WTL) filled with glass fiber (GF) enabled more electromagnetic waves to enter the interior of the composite because of the good impedance of the GFs matching with the air
The shielding effectiveness (SE) performance of the composite material was improved significantly by the layered structure design of GF, carbon fiber (CF) and copper foil combined with fractal layer
Summary
Electromagnetic interference (EMI) shielding materials are widely used in the military, industry, aerospace, and electronics to reduce electromagnetic interference [1]. Carbonyl iron powders (CIPs) are a kind of traditional magnetic loss SE filler with good temperature stability and high magnetic conductivity [7]. Due to their small size, large specific surface. The fractal layer composed of the carbonyl iron powder-filled epoxy (CIP@EP) and the carbon nanotubes-filled epoxy (CNT@EP) was used as an absorbing layer (AL) in the form of a Koch Curve fractal. Koch curve fractal design prepared in this paper shows enhanced EMI shielding performance and a multi-frequency protection effect, which will be one kind of good EMI shielding material
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