High-performance Electromagnetic Interference Shielding Materials Research Articles

Advanced Polymer Composite with Graphene Content for Emi Shielding

One of the increasingly common unexpected outcomes of the extensive usage of electronic devices and systems is electromagnetic interference (EMI). The need for efficient fillers and shielding materials to manage electromagnetic interference (EMI) and associated issues is rising. Adding more filler typically means greater production costs, poor dispersion, and unintended agglomeration, which makes polymer composites harder to work with and mechanically weak. Therefore, it is highly desired to design a strong composite with conductive filler content that nonetheless performs well as an EMI shield. Therefore, using a graphene substrate and dispersion of conducting polymers such as polyacetylene and MWCNT fillers, a hybrid polymer composite based on polyetherimide is proposed in this research. Next, the enhancement of EMI shielding efficiency is examined. The design of the graphene substrate was completed with a coating based on nano filler, and the blending methods of the polymer matrix and the reinforcing filler materials are explored. ANSYS-HFSS software is then used to assess the shield's efficacy among others, and the results demonstrated improved performance. Therefore, by putting the suggested design into practice, high-performance EMI shielding materials can be created by combining various shield fillers. As a result, the composites' mechanical, electrical, and EMI shielding qualities will all improve.

Electromagnetic interference shielding composite aerogels with asymmetric structures developed in aid of neural network

Along with the increasingly serious electromagnetic interference (EMI) pollution, it is in urgent need of exploiting high-performance EMI shielding materials. However, the conventional experimental methods always require a series of tedious preparation and characterization processes, resulting in the long period and high cost. Herein, a fully connected neural network (FCNN) was applied to aid in exploiting silver nanowires/waterborne polyurethan/multi-walled carbon nanotubes (AgNWs/WPU/MWCNTs) EMI shielding aerogels with asymmetric structures to optimize new material evolution and reduce experiment burden. Firstly, the special AgNWs/WPU/MWCNTs aerogels were fabricated with various MWCNTs content (0 wt%, 2 wt%, and 4 wt%) and AgNWs mass (10 mg, 20 mg, 30 mg, and 40 mg) via a combination of directional freezing and spraying procedures, leading to 12 distinct samples. AgNWs/WPU/MWCNTs aerogels hold excellent EMI shielding properties and absorption-dominant shielding mechanism. The experimental EMI shielding effectiveness (SE) data at different frequency were leveraged to establish, train, and test the FCNN model based on Adam optimizer (Adam-FCNN). It is worth noting that Adam-FCNN model predictions are in good accordance with the EMI SE of the physically measured samples, with the lowest root mean square error RMSE of 0.7899, the highest correlation coefficient (R) of 0.9895, and excellent computational efficiency and reliability. Moreover, Adam-FCNN can accurately prognosticate EMI SE of unobtained AgNWs/WPU/MWCNTs aerogels in mechanics-intuitions to reduce repeated preparation and characterizing conditions. Thereby, Adam-FCNN soft model approach opens significant potential for alleviating the experimental burden, accelerating the discovery of innovative materials, and exploring the complex mechanism.

INTERCALATING POLYMER WITH NANO STRATUM GRAPHENE FOR EMI SHIELDING

Electromagnetic interference (EMI) has been identified as one of the ever-increasing unintended consequences of the widespread use of electronic devices and systems. There is a growing demand for effective shielding materials and fillers to control EMI and related concerns. Increased filler content usually results in higher costs, poor dispersion, and unwanted agglomeration, making polymer composites mechanically fragile and difficult to produce. As a result, developing a robust composite with conductive filler content while maintaining good EMI shielding performance is extremely desirable. Hence in this paper, a hybrid polymer composite based on polyetherimide is suggested by dispersion of conducting polymers like polyacetylene and MWCNT fillers with a Graphene substrate. Then the improvement in EMI shielding effectiveness is investigated. The blending techniques of the polymer matrix and the reinforcing filler materials are discussed and the design of the Graphene substrate was done with a nano filler based coating on it. The effectiveness of the shield is then analyzed with ANSYS-HFSS software. S-parameters of the shield like S11, S12, and S21, etc. are determined using the plots obtained and this showed superior performance. Hence by implementing the proposed design the high-performance EMI shielding materials can be fabricated by the combination of different fillers for the shield. This will improve the electrical, mechanical, and EMI shielding properties of the composites.

Effective electromagnetic interference shields based on cellulose nanofibers-carbon nanotubes layered composites

The rapid development of electronic devices and communication technologies has inadvertently led to the production of significant amounts of Electromagnetic Interference (EMI) and radiation, necessitating the development of sustainable, low-density, affordable, and high-performance EMI shielding materials. The present study involves fabricating a layered composite material comprising alternating substrate and conducting layer made primarily of TEMPO-mediated oxidized cellulose nanofibers (TCNF) and carbon nanotubes (CNT). For the substrate layer, TCNF is modified with optimized polydopamine and Fe3+ concentrations to produce mechanically strong film with a tensile modulus of 12.3 GPa. Furthermore, two CNT/TCNF ratios are used in the conducting film: 60% and 80%. In addition to absorption and reflection, the presence of TCNF in the conducting layer creates an impedance mismatch, resulting in a zigzag reflection mechanism for EMI losses. For a thickness of 212 μm, the 5-layered composite exhibited a notable tensile strength of 58 MPa and an efficient EMI shielding effectiveness (EMI SE) of 39 dB in X-band. The prepared composites meet the requirements for a commercial EMI shielding material, namely >20 dB, and outperform the mechanical strength of many other EMI shielding materials.

Co-enhanced electromagnetic shielding and thermoelectric performance in Bi2Te3 coated carbon cloth

Electromagnetic interference (EMI) shielding materials play a crucial role in safeguarding the reliable operation of electronic devices against electromagnetic waves (EW). Nevertheless, electronic devices inherently generate heat, and thermoelectric (TE) can convert heat into electricity, making them attractive as clean energy sources. Therefore, there is an increasing demand for high-performance EMI shielding materials with excellent TE properties. These materials can effectively mitigate EW pollution while simultaneously harnessing heat as electricity. Carbon cloth (CC) as one type of functional textile, has been widely explored as a potential material for EMI shielding, but rarely reported for TE application, due to low Seebeck coefficient. In this study, a facile electrodeposition method was employed to coat Bi2Te3 layers onto the carbon fibers within carbon cloth. This innovative approach not only significantly improved the EMI shielding efficiency from 17.0 dB to an impressive 42.7 dB, but also imparted excellent TE performance to the film, as evidenced by a power factor of 42.4 μWm−1K−2. A four-legged TE module based on this film generates 35.5 nW of power at a temperature difference of 30 K, indicating its significant potential for powering low-consumption wearable electronics after integrating more TE legs. This study has paved the way for the development of a versatile material, that can mitigate EW pollution while simultaneously harnessing heat as electricity, by incorporating high TE performance inorganics into CC using a simple electrodeposition method.

Multifunctional shape memory foam composites integrated with tunable electromagnetic interference shielding and sensing

Porous polymer-based conductive composites are highly regarded for their accomplishments of being applied in the field of electromagnetic interference (EMI) shielding, but fabrication of high-performance porous EMI shielding materials with the ability to realize self-fixable shielding effectiveness (SE) adjustment is still challenging. Herein, ethylene–vinyl acetate copolymer (EVA)@polypyrrole (PPy)@Ag (EPA) foam composites are fabricated by modifying EVA foams with PPy and Ag nanoparticles (AgNPs) in succession. In this system, EVA foam serves as shape memory frameworks to endow this composite with shape memory effect (SME), and PPy is employed to reinforce the interaction between the Ag layers and the EVA foam. Profiting from the reinforced conductive network, the EPA foam composites exhibit electro-thermal performance with a heating temperature of 81.1 °C at a voltage of 1 V and EMI shielding performance with a SE of 107.45 dB within the X-band. Importantly, depending on the SME, the SE of the EPA foams can be easily tuned by controlling and fixing the compressive strain. Moreover, the EPA foams can also serve as sensors for monitoring different actions. By virtue of the above merits, the EPA foams are promising to serve as multifunctional electronics, involving smart EM protection devices and wearable sensors.

Electrical conductivity and electromagnetic interference shielding effectiveness of elastomer composites: Comparative study with various filler systems

This work presents a comparison study of Electrical conductivity and Electromagnetic Interference (EMI) shielding effectiveness (SE) of three different Polydimethylsiloxane (PDMS) composites with randomly embedded Multiwall carbon nanotubes (MWCNTs), Carbon coated iron nanoparticles (FeNPs) and Graphite. The incorporation of these fillers was found to appreciably enhance the electrical conductivity and EMI shielding performance of the composites. The analysis indicated that incorporation of fillers with high aspect ratio gives increased number of conducting pathways, which in turn improved the electrical conductivity and EMI shielding effectiveness of the composites. The 1 wt% MWCNT/PDMS composite displayed electrical conductivity nearly 4 orders of magnitude greater than that of pure PDMS. These composite structures are found to provide numerous interfaces to attenuate the electromagnetic waves, giving rise to an improved shielding mechanism. This work indicates that, creating conductive links within polymer composite structures is a favorable approach to create high-performance EMI shielding materials. The electrical conductivity above 10-6 S/m for all the composites reported here makes them suitable for antistatic coating applications. SEM, X-ray diffraction and Raman spectroscopy were used to analyze the effect of fillers on the PDMS composite structures. The higher filler content composites exhibited an EMI SE level of 20 dB necessary for commercial applications when the films were 1.5 mm thick.

The orientation and inhomogeneous distribution of carbon nanofibers and distinctive internal structure in polymer composites induced by 3D-printing enabling electromagnetic shielding regulation

Carbon nanofiber (CNF)/polycaprolactone (PCL) composites were three-dimention (3D) printed into electromagnetic interference (EMI) shielding parts. 3D-printing process led to an inhomogeneous CNFs distribution in printed composites. The special high-resistance “internal surfaces” introduced between printed threads reduced the conductivity of printed parts and resulted in characteristic secondary percolation phenomena. Meanwhile, the accelerated melt flow in nozzle oriented CNFs in composites along the printing direction, increasing the percolation threshold compared to the random arrangement. As two stage of percolation networks formed, the 3D-printed CNF/PCL parts exhibited excellent EMI shielding performance, with EMI shielding effectiveness value up to 58.7 dB. By controlling the packing density of the printed part, a large number of apertures and heterogeneous interfaces were easily introduced into the interior of parts. It promoted multiple reflection and absorption of electromagnetic waves inside the parts, and enabled adjustment of weight and shielding effectiveness. Therefore, the 3D printing enabled the flexible formation of complex porous structures. From basic materials to designed components, the 3D printing technology can facilitate the transformation of shielding materials into high performance components that are finely designed both internally and externally, making it a promising technology in the field of manufacturing lightweight, high performance EMI shielding materials.

NiFe-doped CoP network-structured nanocomposites for efficient electromagnetic interference shielding

The highly integrated electronics put forward an urgent demand for ultrathin and high-performance electromagnetic interference (EMI) shielding materials. Herein, NiFe doped CoP network-structured nanocomposites support on titanium mesh were prepared by hydrothermal method, the resulting composites with EMI SE of 63.9 dB at 150 µm thickness exhibit excellent EMI shielding performance. Neat flower-like CoP and NiFe nanoparticles are tightly attached to the surface of titanium mesh, while NiFe doped CoP exhibits loose needle-like structure accompanied by nanoparticles attachment. The resulting reticulated nanocomposites show efficient EMI shielding mainly based on absorption loss. CoP with good conductivity promotes the dielectric loss of electromagnetic waves, the penetration of magnetic NiFe strengthens the impedance of the composites, and the synergistic effect of CoP and NiFe with loose structure are conducive to further absorption and attenuation of electromagnetic waves, thus titanium mesh based NiFe-doped CoP composites possess excellent EMI shielding. These high-performance ultrathin EMI shielding materials would show superior application prospects in electronics and electrical appliances.

Synthesis of high-quality vertical graphene nanowalls on metal foams and their applications in EMI shielding

Due to the development of high-frequency electronic devices, electromagnetic pollution has attracted global attention. Electromagnetic interference (EMI) shielding materials with low thickness, improved EMI shielding performance and lightweight are highly required for protecting the devices. Metal foams (MFs) and carbon-related materials have been successfully applied in EMI shielding. Herein, by utilizing the plasma-enhanced chemical vapor deposition (PECVD) method, high-quality vertical graphene nanowalls (VGNs) were prepared on Cu foam (CF) and Ni foam (NF) substrates. The combination of porous VGNs and MFs significantly improved their electrical conductivity, thus their EMI shielding performance was enhanced. The electrical conductivity of the VGNs/CF films could reach 4.81 × 106 S·m-1, increased by 15.3 % compared with the pristine CF films. At a frequency range of 8.2–12.4 GHz, the EMI shielding effectiveness values of VGNs/CF films with a thickness of ∼ 120 µm could reach 81.7 dB, increased by 25.9% compared with the pristine CF films. The VGNs/MF composite films with preferable EMI shielding effectiveness provide a new possibility for developing high-performance EMI shielding materials.

Progress in the Foaming of Polymer-based Electromagnetic Interference Shielding Composites by Supercritical CO2.

As a critical action plan formulated for peaking carbon dioxide emissions, polymeric electromagnetic interference (EMI) shielding materials based on CO2 foaming technology have recently been attracting widespread attention in both research and industry, attributable to their efficient use of CO2 , high specific strength, corrosion resistance and low-cost characteristics. In the past decade, the emergence of novel design concepts and preparation techniques for CO2 foaming technology has led to the development of new high-performance EMI shielding materials in this field. This review summarizes the research progress made to date on the fabrication of EMI shielding composite foams by supercritical carbon dioxide (scCO2 ) foaming. We also explore the structure-activity relationships between the component/distribution and EMI shielding properties. Additionally, the application prospects and development challenges of new EMI shielding composite foams are described.

Flexible and High-Performance Electromagnetic Shielding Materials from Waste Polyurethane Foams

In the modern society, polymer composites utilizing various wastes for electromagnetic interference (EMI) shielding are of great economic and social significance. Herein, we report that waste polyurethane foams (WPUF) can be facilely converted into high-performance EMI shielding materials via surface coating of carbon nanotubes followed by hot pressing. The merit of this work lies in the novel skin-core segregated structure from the complete three-dimensional skeleton of WPUF, which is well retained after compression molding. The uniform distribution of multiwalled carbon nanotubes (MWCNTs) on the polyurethane skeleton surface assisted by cellulose nanofibers (CNFs) provides the material with remarkable electrical conductivity, leading to excellent EMI shielding properties. The resultant composite (WPUF-MC) achieves a high EMI shielding effectiveness (SE) of 63.2 dB at a low loading of MWCNTs (6.6 wt %), far surpassing the values for many early reported shielding materials of this kind. Moreover, the WPUF-MC also exhibits sufficient flexibility and reliable EMI shielding performance. Even if bent or twisted 1000 times, it can still maintain EMI SE at a fairly high level. This work not only offers an effective strategy for high-value utilization of WPUF but also may expand the application potential of flexible shielding materials.

Gradient structure silicone rubber composites for selective electromagnetic interference shielding enhancement and low reflection

Electromagnetic interference (EMI) shielding composites with gradient filler distributions were fabricated with the application of an induced magnetic field. The selective enrichment of nickel-coated carbon fibers within a core-shell structure effectively strengthens the overlap between fillers. This composite exhibited outstanding conductivities (98.2 S/m) that were two orders of magnitude greater than composites that possessed uniformly dispersed fillers because of the favorable inductive effect and the perfect loading of Ni nanoparticles. In addition, the sandwich structure causes the electromagnetic (EM) waves to reflect multiple times, further improving the EMI shielding effectiveness (SE) of the composite and resulting in a maximum SE of 60.8 dB. The introduction of magnetic Fe3O4@MWCNTs greatly increased the EM wave absorption efficiency from 14% to 45%, which resulted in low reflection peaks due to the resonant cancellation of the incident and reflected EM waves. The reflectivity of the composite was only 4% at 8.2 GHz, indicating a high absorption rate of 96% at this frequency. Furthermore, the composite shows excellent EMI shielding stability after 1000 repeated bends. This work thus describes a new approach to the preparation of high-performance (high-efficiency and low-reflectivity) EMI shielding materials and broadens their applicability to precision electronic devices and flexible wearable devices.

Methylene blue adsorption derived thermal insulating N, S-co-doped TiC/carbon hybrid aerogel for high-efficient absorption-dominant electromagnetic interference shielding

The development of absorption-dominant electromagnetic interference (EMI) shielding materials with high-efficiency EMI shielding effectiveness (SE) and low reflection (R) is crucial but challenging for next-generation electronics devices and telecommunication. In this regard, a facile and environmentally friendly approach was proposed to fabricate N, S-co-doped TiC/carbon hybrid aerogels with hierarchically porous architecture through MXene/cellulose hybrid hydrogels as precursors for adsorbing dyes, followed by freeze drying and carbonization process. Profiting from the synergistic effect of highly interconnected three-dimensional (3D) porous structure, heterogeneous conductive network with greatly conductive difference as well as heteroatoms-doping induced dipole polarization, the resultant aerogel with an ultra-low density (47.1 mg/cm3) achieves a highly efficient EMI SE of 84.3 dB at 12.4 GHz (average 81.8 dB in the X-band) and a superior absorption coefficient of 0.68 simultaneously. Meanwhile, the highly porous structure endows the prepared aerogels with outstanding thermal insulating capacity, which is essential to provide infrared stealth and radar stealth for military equipment and to protect sensitive electronic devices from high-temperature attacks. This work offers a prospective strategy for constructing high-performance absorption-dominated EMI shielding materials with excellent thermal insulation properties, and the obtained aerogels present broad application prospects in the fields of aviation, portable electronic equipment and national defense industry.

Promising PVDF-CNT-Graphene-NiCo chains composite films with excellent electromagnetic interference shielding performance

Polymer-based composite electromagnetic interference (EMI) shielding materials have aroused great interest among scientific researchers because of excellent properties. Herein, the poly(vinylidene fluoride) (PVDF)-carbon nanotube (CNT)-Graphene (G)-NiCo chains composite film with ultrahigh EMI shielding properties was prepared through solution mixing and compression molding. In the composite film, 1D carbon nanotube (CNT) and NiCo chains connected the surrounding 2D graphene nanoplates and formed interfacial interconnected networks. The electrical conductivity and total electromagnetic interference shielding effectiveness (EMI SE T ) of the samples increased progressively with the increased NiCo quality contents. The resultant PVDF-CNT-G-8NiCo composite film exhibited an excellent electrical conductivity of 9.12 S/cm and an ultrahigh EMI SE T of 63.3 dB. The results were superior to those of PVDF-CNT-8NiCo composite film, clearly confirming the synergistic effect of graphene nanoplates and CNT. The formation of multi-layers interfacial conductive CNT-G-NiCo networks promoted conductive dissipation, multiple reflections and scattering of incident electromagnetic (EM) waves. Meanwhile, this work provides guidance for the rational design of high-performance polymer-based composite EMI shielding materials and has great potential in practical applications. • PVDF-CNT-Graphene-NiCo chains composite film was prepared. • The synergistic effect of CNT, graphene and NiCo alloy formed interconnected networks. • The multi-layers networks promoted conductive dissipation, and multiple scattering of EM waves. • A superior EMI SE T of 63.3 dB were achieved in PVDF-CNT-G-8NiCo composite film.

Absorption dominated high-performance electromagnetic interference shielding epoxy/functionalized reduced graphene oxide/Ni-chains microcellular foam with asymmetric conductive structure

In order to develop high-performance electromagnetic interference (EMI) shielding materials for the increasingly complex electromagnetic (EM) environment, in this work, the epoxy/functionalized reduced graphene oxide/Ni-chains microcellular foams with asymmetrical conductive structure (a-EP/f-RGO/Ni-chains microcellular foams) are prepared through a thermal compressing method and then followed by a supercritical carbon dioxide (scCO2) foaming process. Benefiting from the construction of asymmetrical conductive structure which is assembled from the f-RGO-rich layer and Ni-chains-rich layer, the a-EP/f-RGO/Ni-chains microcellular foam with 5 vol% f-RGO and 5 vol% Ni-chains content exhibits better electrical conductivity of ∼10−1 S/m and higher EMI shielding effectiveness (EMI SE) of 40.82 dB in X-band compared with the homogeneous conductive structured EP/f-RGO/Ni-chains (h-EP/f-RGO/Ni-chains) microcellular foam in same filler content. In addition, the maximum difference of reflection coefficient (R) up to ∼0.5 is achieved by actively regulating the EMI shielding process from reflection-absorption to absorption-reflection-reabsorption in different directions of EM wave incidence on the foams. Moreover, the compressive strength of microcellular foam is up to 24.58 MPa. Combined with excellent EMI shielding property and outstanding compressive property, the a-EP/f-RGO/Ni-chains microcellular foams prepared in this work display significant application advantages as high-performance EMI shielding materials.

Hydrophobic, flexible electromagnetic interference shielding films derived from hydrolysate of waste leather scraps

With the rapid development of wireless telecommunication technologies, it is of fundamental and technological significance to design and engineer high-performance shielding materials against electromagnetic interference (EMI). Herein, a three-step procedure is developed to produce hydrophobic, flexible nanofiber films for EMI shielding and pressure sensing based on hydrolysate of waste leather scraps (HWLS): (i) electrospinning preparation of HWLS/polyacrylonitrile (PAN) nanofiber films, (ii) adsorption of silver nanowires (AgNWs) onto HWLS/PAN nanofiber films, and (iii) coating of HWLS/PAN/AgNWs nanofiber films with polydimethylsiloxane (PDMS). Scanning electron microscopy studies show that AgNWs are interweaved with HWLS/PAN nanofibers to form a conductive network, exhibiting an electrical conductivity of 105 S m−1 and shielding efficiency of 65 dB for a 150 μm-thick HWLS/PAN/AgNWs film. The HWLS/PAN/AgNWs/PDMS film displays an even better electromagnetic shielding efficiency of 80 dB and a water contact angle of 132.5°. Results from this study highlight the unique potential of leather solid wastes for the production of high-performance, environmentally friendly, and low-cost EMI shielding materials.

Metallic fusion of nanocrystal thin films for flexible and high-performance electromagnetic interference shielding materials

Low-cost flexible electromagnetic interference (EMI) shielding materials are attracting considerable attention because of the rapid development of wearable smart electronics, such as wearable health monitoring systems, and flexible energy storage and harvesting systems. In the present study, we developed ultrathin, flexible, and high-performance EMI shielding materials using Ag nanocrystals (NCs) through low-cost, room-temperature wet chemical processes conducted at atmospheric pressure. Sequential ligand-exchange and reduction processes not only substantially reduced the distance between the Ag NCs but also induced intensive metallic fusion of the Ag NCs, resulting in large-scale three-dimensional interconnected conductive pathways. The fused Ag NC thin films exhibited high electrical conductivity (∼24,000 S/cm for a film ∼800 nm thick) and outstanding mechanical stability, offering stable EMI shielding performance over 1000 cycles of various mechanical deformations, including twisting, crumpling, and folding. In addition, compared with most previously reported solution-based materials, our Ag NC thin films demonstrated an excellent EMI shielding effectiveness value of ∼60 dB in the X-band range 8.2–12.2 GHz at much thinner thickness (∼1.3 μm). With the advantages of easy processing, good mechanical flexibility, and high-performance EMI shielding, the fused NC thin films developed in the present work represent innovative potential EMI shielding materials for next-generation wearable smart electronics.

In-situ metallized carbon nanotubes/poly(styrene-butadiene-styrene) (CNTs/SBS) foam for electromagnetic interference shielding

The porous conductive polymer composites have received great attention owing to their superiority of being utilized in electromagnetic interference (EMI) shielding applications. Herein, lightweight and highly compressible conductive composite foam composed of poly(styrene-block-butadiene-block-styrene) (SBS) polymer matrix, carbon nanotubes (CNTs) and silver nanoparticles (Ag NPs) is fabricated by freeze-drying technology, silver precursor absorption and in-situ reduction process. Three-dimensional CNTs conductive network and partially embedded Ag NPs synergistically endow the foam with excellent mechanical, electrical and EMI shielding performance. The flexible 8Ag/4CNTs/10SBS composite foam with a low density of 0.42 g/cm3 exhibits moderate compressive strength of 169.2 kPa at strain of 50%, remarkable conductivity of 753 S/m, and prominent EMI shielding effectiveness (SE) value of around 91 dB in the electromagnetic wave frequency range of 8.2–12.5 GHz. In addition, the 4Ag/4CNTs/10SBS composite foam exhibits robust mechanical–electrical property upon 1000 compression-release cycles at strain of 50%, and its SE value increased by about 33% compared with the initial state after the cyclic compression test. These results suggest that the Ag/CNTs/SBS foams possess promising potential to be used as lightweight, flexible, and high-performance EMI shielding materials in modern electronic devices.

Electromagnetic interference shielding anisotropy enhanced by CFRP laminated structures

Continuous carbon fiber reinforced polymers (CFRP) composites, particularly prepreg stacked composites, have anisotropic properties, including anisotropy of electrical conductivity and dielectric characteristics. These features lead to electromagnetic interference (EMI) shielding anisotropy of the CFRP. The coaxial transmission line method was used to test the EMI shielding of CFRP to clarify the EMI shielding anisotropy of CFRP. Moreover, the optimization of EMI shielding performance of CFRP by changing the composites’ structure were also investigated systematically. The anisotropy of EMI shielding was confirmed for the first time by the coaxial transmission line method. The results showed that a quasi-radial sample had the highest shielding effectiveness (25.8 dB) at 15 GHz, and the carbon fibers in this sample aligned in the direction of the electric field of electromagnetic waves. The orientation of fibers relative to the direction of electric field clearly affected the EMI shielding performance of the CFRP composites. The four-ply CFRP (0°/90°/0°/90°) with three cross-layers had the excellent shielding value of 28.9 dB at 15 GHz, that was far superior to that of a unidirectional CFRP (0°/0°/0°/0°) composite (SE = 18.6 dB), and it even outperformed an eight-ply unidirectional CFRP composite (SE = 22.6 dB). Laminated structures governed SE, and the number of cross-layers in the composites improved their EMI shielding performance. The shielding mechanisms of cross-layer CFRPs were also discussed and clarified based on both experimental and theoretical analysis. We believe that these findings could provide a scientific basis and potential in designing high-performance EMI shielding materials.