Using carbon-fibre-reinforced polymer (CFRP) composites for electromagnetic interference (EMI) shielding has become a rapidly emerging field. This state-of-the-art review summarises all the recent research advancements in the field of electromagnetic shielding properties of CFRP composites, with exclusive attention paid to experimental work. It focuses on (1) important mechanisms and physical phenomena in the shielding process for anisotropic carbon-fibre composites and (2) shielding performance of CFRP materials as reported in the literature, with important performance-affecting parameters. The key properties which directly influence the shielding performance are identified, the most critical being the carbon-fibre concentration along with length for discontinuous carbon-fibre-filled polymers and the lay-up for continuous carbon-fibre-reinforced composites. The effect of adding conductive inclusions such as metal or carbon nanotubes is also reviewed. It is emphasised that processing conditions are strongly linked with the shielding properties of a composite. This is a first review, which covers all the recent advancements in the field of shielding properties of carbon-fibre-reinforced composites, with detailed analysis of factors influencing these properties and clear distinction between continuous and discontinuous reinforcement. It is shown that CFRP composites make a good candidate as an EMI shielding enclosure material.

In order to improve the interfacial property of carbon fiber composites, the carbon fiber was pretreated by plasma technique and then coated with polypyrrole (PPy) by chemical oxidation polymerization of pyrrole. The surface modified carbon fiber and composite were characterized by SEM, AFM, XPS, FT-IR and IFSS. Results show that the interfacial shear strength of the modified single fiber increased by 259.3%, which may be ascribed to that the plasma pretreatment can increase the amount of polar groups on the surface of the carbon fiber, and facilitate the formation of hydrogen bonds between the carbon fiber and PPy, thus enhancing the interfacial property of the composite PPy-carbon fiber/epoxy.

应用等离子体技术对碳纤维(CF)表面进行预处理,然后进行液相沉积聚吡咯处理。使用X射线光电子能谱仪、原子力显微镜(AFM)、扫描电子显微镜(SEM)和傅立叶红外光谱仪等手段对碳纤维表面形态和结构进行分析与表征,并进行单纤维界面剪切强度试验和SEM观测,研究了碳纤维复合材料的界面粘结性能。结果表明,等离子体预处理碳纤维沉积聚吡咯(PPy)使单纤维界面剪切强度提高了259.3%。分析结果表明,界面剪切强度的提高与纤维/树脂间的机械铆合和界面的作用力有关。等离子体预处理使碳纤维表面的羧基基团增多,在羧基和PPy之间形成氢键,从而提高了碳纤维复合材料的界面性能。

Graphene/carbon fiber/epoxy composites were prepared by autoclave co-curing molding process with graphene prepregs as the functional layer, which were paved on the surface of carbon fiber perform. The effect of graphene prepregs on the internal quality, electromagnetic interference shielding performance and mechanical properties of the composites was investigated by ultrasound scanner, metallograph, four-probe instrument, vector network analyzer and electronic universal material testing machine. The results show that the internal quality of the graphene/carbon fiber/epoxy composites will not be influenced by the addition of graphene prepregs, and there are a good interfacial compatibility between graphene functional layer and carbon fiber structural layer. On this basis, graphene prepregs, which serves as the functional layer, taking advantage of excellent electrical conductivity, can improve the electromagnetic interference shielding performance of the corresponding composites rapidly. With only one layer of graphene prepreg (G105/3234), electromagnetic interference shielding efficiency of carbon fiber/epoxy composites is improved from 27.7 dB to 64.7 dB. Meanwhile, the obtained composites still maintain satisfactory mechanical properties.

CFRP composites are widely used in aerospace due to their excellent mechanical properties, however, due to the anisotropy of the individual plies, the electro magnetic interference(EMI) shielding efficiency(SE) for vertically polarized waves of the unidirectional fiber laminates is poor. In order to protect electronics within these equipments from increasingly severe electromagnetic interference, it is particularly important to enhance the electromagnetic shielding efficiency of the CFRP. In this paper, Al particles were introduced and a conductive network was constructed in the CFRP interlaminar region by condensing the Al particles on the prepreg surface. The effects of different Al particle contents on EMI SE and mechanical properties of composites were studied. With the increase of Al particle contents, the electrical conductivity and the EMI SE of CFRP composites increase. When the Al mass fraction in the resin is 33.3%, the in-plane conductivity of the composites increases by 3 orders of magnitude, the EMI SE of the Al particle sandwich CFRP composites is improved by more than 10 dB in the frequency range of 3-17 GHz. With the increase of Al particle contents, the interlaminar shear strength and bending strength of the composites increase first and then decrease. When the Al mass fraction in the resin is 33.3%, the interlaminar shear strength (ILSS) of the composites increases by 5.2% to 80.5 MPa, and when the Al mass fraction in the resin is 50%, the bending strength of the composites increases by 20% to 1441.0 MPa and the bending modulus increases by 10.2% to 101.83 GPa. It can be seen that the mechanical properties and electromagnetic shielding effectiveness of the Al particles sandwich CFRP composite can be improved simutaneously.It is a kind of structure electromagnetic shielding integrated composite with broad application prospects.

Tremendous development in electronic devices and their indiscriminate use has created a severe problem of electromagnetic pollution. Different types of electromagnetic interference (EMI) shielding materials and structures are used to protect electronic devices from the harmful effect of electromagnetic pollution. A present study was conducted to compare the effect of dielectric and magnetic nanofillers on electromagnetic shielding effectiveness (EMI SE) of carbon fiber reinforced composite structures (CFRC). Composites structures were developed using different dielectric and magnetic nanofillers. Effect of nanofillers on microwave absorption properties and reduction in electromagnetic pollution was investigated. Relationship between electrical conductivity and EMI shielding effectiveness in L, S, C, and X-frequency range was also studied. Among the dielectric nanofillers, silicon carbide showed excellent EMI SE in X-frequency range, while among magnetic nanofillers, zinc oxide showed excellent EMI shielding characteristics in a broad frequency range of 100 MHz to 13.6 GHz. Among magnetic nanofillers, CFRC with zinc oxide nanofillers showed the lowest skin depth value of 3.32 × 10−4 mm and among dielectric nanofiller, CFRC with silicon carbide nanofillers gave the lowest skin depth value of 6.49 × 10−4 mm, implying their excellent potential in EMI shielding applications.

In this work, we have attempted to improve electromagnetic interference (EMI) shielding and mechanical behavior of epoxy/carbon fiber (CF) composite, simultaneously, in the presence of functionalized carbon nanotubes. It is well understood that properties of composite depend on the interface between the filler and matrix. Considering this basic understanding, functionalized carbon nanotubes/epoxy nanocomposites were impregnated into a bidirectional carbon fiber (CF) mat and, further, various mechanical and EMI shielding behaviors were studied. Multiwalled carbon nanotubes were functionalized with branched poly(ethyleneimine) (b-MWNT) to tailor the interface of epoxy/CF composites. Laminates with two layers of CF were fabricated with functional MWNT modified epoxy. Scanning electron microscopy was used to analyze the microstructure of epoxy/CF laminates. Lap shear test was performed to analyze adhesion between the modified epoxy and carbon fiber. Further dynamic mechanical analysis in the temperature range of 30-160 °C was performed. Thermal degradation of composites was studied using a thermogravimetric analyzer. Electrical conductivity of laminates was measured using a four-point method on an Agilent probe station. EMI shielding effectiveness (SE) was measured for 0.5 mm-thin laminates in the Ku band. The b-MWNT modified epoxy/CF composites showed excellent SE of ca. -60 dB and SE of ca. -50 dB, which are of commercial importance. Compared to unmodified epoxy/CF, b-MWNTs/epoxy/CF exhibited 200% increment in EMI SE and 35% enhancement in storage modulus due to the improved interface between the epoxy matrix and carbon fiber.

A metal-organic framework (MOF) based on a conjugated organic ligand and a transition-metal ion was designed and used to construct a novel multiwalled carbon nanotube (MWNT)/MOF interphase via hierarchical assembly on the carbon fiber (CF) surface and was compared to various interphases established by MWNT and MOF. An intertwined MWNT and MOF "jujube core" was randomly dispersed on MWNT@CF and MOF@CF surfaces, while interpenetrating structures with the MWNT network and MOF jujube core were simultaneously observed on MWNT/MOF@CF due to coordination bonds and π-π conjugation effects, which were derived from the MWNT template with carboxyl groups and sp-hybridized domains as well as the secondary growth of MOF to promote self-assembly and the connection of MOF. The transverse fiber bundle test (TFBT) strength and interfacial shear strength (IFSS) of the MWNT/MOF@CF composite were 36.9, 6.1, and 20.8%, 16.3% higher than those of MWNT@CF and MOF@CF composites, which were attributed to the smoothed modulus transition of the stiffening interphase formed by the MWNT/MOF hybrid structure as "armor" to effectively buffer the stress transfer between a carbon fiber and the resin matrix. Compared to MWNT@CF and MOF@CF composites, MWNT/MOF@CF composites had the highest EMI shielding effectiveness, which was attributed to the combined effects of multiple reflections, conductive loss, and interface polarization from the interpenetrating MWNT/MOF hybrid structures, which realized the integration of the structure and function of the carbon fiber composites.

Efficient design of electromagnetic (EM) shielding materials has emerged as a challenging research area in the past decade. To address this issue, we propose thin, lightweight, yet strong epoxy/carbon fiber (CF) composites modified with functionalized graphene oxide (GO) sheets as "interconnects". This strategy resulted in an impressive 175% improvement in the storage modulus, a 100% enhancement in the lap shear strength, and an extraordinary 200% improvement in the shielding effectiveness at a very low GO content (0.5 wt %). First, GO was functionalized with an epoxy prepolymer (namely E-f-GO) to improve the interfacial adhesion with the matrix polymer, epoxy. As a control, epoxy nanocomposites were also prepared with modified GO. It was followed by the fabrication of CF laminates impregnated with epoxy nanocomposites. Covalent functionalization of epoxy chains on GO sheets was confirmed using various techniques like X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, and thermogravimetric analysis. Epoxy nanocomposites were analyzed for thermal, mechanical, electrical, and adhesive strength behavior. CF laminates with epoxy nanocomposites were fabricated using vacuum-assisted resin transfer molding. The E-f-GO/epoxy/CF composite exhibited an excellent shielding effectiveness value of -70 dB, and the storage modulus was found to be >40 GPa. The modified composite showed absorption-driven shielding of EM waves and hence can be used as a highly effective EM absorber.

Functional polymer composites are in huge demand in electronic industry in general and for electromagnetic interference shielding in particular, due to ease of processing, design flexibility and lightweight. Herein, efforts are made to enhance electromagnetic interference shielding effectiveness in epoxy/carbon fiber composite, by electrodepositing magnetic particles on the surface of carbon fiber. This approach results in 100% enhancement in shielding effectiveness with respect to epoxy/Carbon fiber composites. Electrodeposition, an industrially viable and a scalable technique, is adopted here to obtain nickel decorated carbon fiber. Various nickel deposited carbon fiber morphologies are obtained by varying the applied current. Various microstructures of nickel deposited carbon fiber are obtained and the final parameters are fixed. Further, X-ray diffraction confirms the presence of nickel on the carbon fiber surface. In addition magnetic, electrical, thermal behaviour of nickel deposited carbon fiber is evaluated systematically. Epoxy/carbon fiber composites are fabricated using vacuum assisted resin transfer moulding technique. 2-Layered sandwich structure is prepared with layer 1 as nickel deposited carbon fiber and layer 2 as only carbon fiber. EMI shielding effectiveness is measured in the frequency range of 12-18 GHz. Epoxy with nickel deposited carbon fiber and bare carbon fiber sandwich architecture showed excellent shielding effectiveness up to 50 dB and with maximum absorption of up to 40 dB at 15 GHz. Thermal studies are also carried out to understand the materials response at higher temperature and frequency. Such thin, light-weight, excellent EM absorbers can be used as EMI enclosures for battery casings of hybrid electric vehicles, communication systems etc.

With the aim to obtain enhanced absorbing performance at small thickness and low filling, a robust strategy to fabricate zinc oxide (ZnO) modified carbon fiber (CF) structures have been successfully prepared by using low temperature hydrothermal method. Due to the multi-interface polarization caused by the high specific surface area of the complex heterostructures and the improvement of impedance matching, the composites show excellent electromagnetic wave absorption properties. Under the condition of low filling content (20 wt%) and ultra-thin thickness (1.5 mm), the excellent absorption performance of minimal reflection loss of -34.4 dB and an effective absorption bandwidth (RL ≤ -10 dB) of 4.94 GHz is achieved. In addition, the effective absorption bandwidth covers the whole 2-18 GHz band with the increase of thickness from 0.5 to 10 mm. This work provides an innovative method for designing the matching layer of carbon-based absorbing materials, and ZnO@CF heterostructure is expected to become a potential absorbing material.

A single-wall carbon nanotube (SWCNT) has superior optical, electrical, and mechanical properties due to its unique structure and is therefore expected to be able to form flexible high-performance transparent conductive films (TCFs). However, the optoelectronic performance of these films needs to be improved to meet the requirements of many devices. The electrical resistivity of SWCNT TCFs is mainly determined by the intrinsic resistivity of individual SWCNTs and their junction resistance in networks. We analyze these key factors and focus on the optimization of SWCNTs and their networks, which include the diameter, length, crystallinity and electrical type of the SWCNTs, and the bundle size and interconnects in networks, as well as chemical doping and microgrid design. We conclude that isolated/small-bundle, heavily doped metallic or semiconducting SWCNTs with a large diameter, long length and high crystallinity are necessary to fabricate high-performance SWCNT TCFs. A simple, controllable way to construct macroscopic SWCNT networks with Y-type connections, welded junctions or microgrid design is important in achieving a low resistivity. Finally, some insights into the key challenges in the manufacture and use of SWCNT TCFs and their prospects are presented, hoping to shed light on promoting the practical application of SWCNT TCFs in future flexible and stretchable optoelectronics.