Shielding Effectiveness Test Research Articles

An Experimental Study on Electromagnetic Shielding Effectiveness and Impact Resistance of UHPC for Protective Facilities

The research was conducted on incorporating short carbon fiber and multi-layer graphene into ultra-high performance concrete (UHPC) to improve the dynamic mechanical performance and electromagnetic shielding effectiveness (SE). In the electromagnetic shielding effectiveness testing, the results shown that UHPC with uniformly distributed conductive fibers exhibited superior shielding effectiveness at high frequencies. In comparison to normal concrete, the UHPC demonstrated the capability to withstand higher impact energy. Simultaneously enhancing both electromagnetic shielding characteristics and dynamic mechanical performance of cementitious materials can be challenging. In this study, employing a composite structure was effective solution to overcome this issue. In accordance with the experimental results, a scaled testing protective facility has been constructed, and the research results could provide the reference for the design and construction of protective structures.

Design of an Integrated Switching Antenna for Shielding Effectiveness Testing of Small Enclosures From 1 MHz to 100 MHz

Design of an Integrated Switching Antenna for Shielding Effectiveness Testing of Small Enclosures From 1 MHz to 100 MHz

Electromagnetic Shielding Effectiveness and Impact Test Performance of Carbon Fiber Reinforced Polymer Composites with Hematite and Goethite

AbstractCarbon fibers (CFs) are versatile materials widely employed in carbon fiber‐reinforced polymer (CFRP) composites, known for their superior mechanical properties and electromagnetic interference (EMI) shielding capabilities. This study focuses on the successful production of 2‐layer CFRP composites reinforced with hematite (Fe2O3) particles, in two different sizes (≈44 µm (325 mesh) and 50 nm), and goethite (FeO(OH)), utilizing the hand lay‐up method. The investigation encompasses EMI shielding effectiveness (SE) within a frequency range of 700 to 6000 MHz, and the drop‐impact strength resistance properties (under a 6 J load). Results indicate that the highest EMI SE value, 60.19 dB at 5900 MHz, is achieved with 5 wt.% goethite reinforcements, while with a reduction in drop‐impact strength. For hematite‐reinforced composites, the highest EMI SE, measuring 57.85 dB at 5800 MHz, is observed for samples containing 15 wt.% hematite particles with a size of 50 nm, which exhibited an overall improvement in impact strength compared to non‐reinforced samples. This research highlights the potential of these CFRP composites for EMI shielding applications, with considerations for their impact on mechanical properties, providing valuable insights for applications demanding both EMI protection and structural integrity.

Influencing factors of shielding effectiveness test of electromagnetic shielding clothing

There is no perfect method to test and evaluate electromagnetic shielding (EMS) clothing up to now. The main reason is that the influence laws of the emission source parameters and the test position on the shielding effectiveness (SE) of the EMS clothing has not been clarified. In this paper, the SE of the EMS clothing is tested using a semi anechoic chamber in the frequency range of 1–18 GHz. The variation of the SE of the clothing is explored when the emission source parameters and the test positions are different. It is found that the SE of the EMS clothing decreases obviously with the increase of the testing distance, and the decline degrees are different with different frequencies. The decline trend slows down and approaches stability as the distance increases to a certain extent. The influence of the emission source angle on the SE is closely related to the frequency and positive or negative effects are produced at different frequency points. The SE are low when the test points are in the leakage areas with seams and openings, and the SE are high in the normal area. Under certain conditions, the measured SE of the clothing is close to zero or even less than zero. That is, a dangerous frequency point is formed. The mechanism of the above-mentioned laws is analyzed, and a new multi-index composite evaluation method is proposed to scientifically evaluate the EMS clothing based on the comprehensive consideration of the influencing factors. This research has great significance to promote the scientific test, evaluation and relevant standard formulation of the EMS clothing, and provides a reference role for the design and production of the EMS clothing.

EMI Shielding and Absorption of Electroconductive Textiles with PANI and PPy Conductive Polymers and Numerical Model Approach

The paper presents the results and analysis of interdisciplinary research concerning electromagnetic field shielding, conductive polymers printed on textiles and numerical simulation using the finite element method (FEM). The use of conductive, layered textiles for shielding electromagnetic interference (EMI) has been proposed. After establishing the optimal conditions for deposition of polyaniline (PANI) and polypyrrole (PPy) on polyacrylonitrile (PAN) fabric, conductive composites were made by means of reactive inkjet printing. For this purpose, polyacrylonitrile (PAN) fabrics were coated with polyaniline or polypyrrole, obtained by chemical oxidation of aniline hydrochloride and pyrrole by ammonium peroxydisulfate. The morphology of the obtained coatings was observed using a scanning electron microscope (SEM). The conductive properties (surface resistance) of the fabrics were measured using the four-wire method, and the tests of the effectiveness of electromagnetic shielding were carried out using the waveguide method in the frequency range from 2.5 to 18 GHz. The results of experimental shielding effectiveness (SE) tests and numerical simulation showed that the composites of polyacrylonitrile with polyaniline PAN/PANI and polyacrylonitrile with polypyrrole PAN/PPy achieved very good and good EMI shielding efficiency, respectively. Moreover, the obtained measurement results were verified by numerical modeling with the use of FEM–ANSYS HFFS software.

Electrical Conductivity and Electromagnetic Shielding Effectiveness of Bio-Composites

In this paper, the electrical conductivity and electromagnetic shielding effectiveness of two bio-composites are studied by experimental testing and numerical models. Two monolithic composites with partly bio-based content were manufactured. The first bio-composite is made of a carbon fiber fabric prepreg and a partly bio-based (rosin) epoxy resin (CF/Rosin). The second bio-composite is a combination of prepregs of carbon fiber fabric/epoxy resin and flax fiber fabric/epoxy resin (CF-Flax/Epoxy). A single line infusion process was used prior to the curing step in the autoclave. Both variants are exemplary for the possibility of introducing bio-based materials in high performance CFRP. In-plane and out-of-plane electrical conductivity tests were conducted according to Airbus standards AITM2 0064 and AITM2 0065, respectively. Electromagnetic shielding effectiveness tests were conducted based on the standard ASTM D 4935-10. Materials were prepared at the German Aerospace Center (DLR), while characterization tests were conducted at the University of Patras. In addition to the tests, numerical models of representative volume elements were developed, using the DIGIMAT software, to predict the electrical conductivity of the two bio-composites. The preliminary numerical results show a good agreement with the experimental results.

FABRICS FOR BUILDTECH ELECTROMAGNETIC SHIELDS BASED ON MAGNETRON SPUTTERING DEPOSITION

Electromagnetic radiation may cause interference for the proper functioning of electronic equipment and risks for human’s health. Protection against the hazards of EM radiation on various frequencies may be achieved by flexible textile fabrics with electrical conductive properties. A novel technology for imparting conductive properties to fabrics is utilizing magnetron sputtering of metallic thin films. This research focuses on plasma coated fabrics with three types of metallic layers: Nick el, Chrome and Titanium. PES woven fabrics of 88 g/m2 were coated by plasma magnetron sputtering with these three types of metals. Coating was performed on both sides of the fabric with a thickness of 400 nm. SEM images provedmetal deposition on the fiber surface, while atomic absorption tests showed the content of deposited metal. Linear resistance of coated fabrics was measured with Ohmmeter for a preliminary check of electric conductivity of the achieved fabrics. Electromagnetic shielding effectiveness tests showed a slight increase of EMSE above the noise level in the frequency range of 100-1000 MHz, of 2- 3 dB. The research studies will continue to improve shielding effectiveness of plasma coated fabrics for electromagnetic shielding

An EMC control method for large-diameter radio telescope

The large-diameter radio telescope has extremely high system sensitivity; however, various electronic devices will be equipped at the constructing and operating process, which will generate electromagnetic interference impacting on radio astronomical observations. Therefore, it is necessary to investigate effective Electromagnetic Compatibility (EMC) control approach. This paper based the EMC requirements of radio astronomy, analyzing the deficiencies and adaptability of the EMC evaluation standards available, considering the feasibility of engineering process and operating management as well, on which an EMC control method for large-diameter radio telescope was proposed, including quantified interference level limits for the electronic equipment, EMC measurement method and shielding effectiveness testing method. This method will be applied to the proposed steerable 110-m aperture radio telescope (Qi Tai Radio Telescope, QTT) in Xinjiang, ensuring that QTT has good EMC performance.

Effect of double-layer composite absorbing coating on shielding effectiveness of electromagnetic shielding fabric

In order to meet the demand for high-performance electromagnetic shielding fabrics, using absorbing coatings to improve the shielding effectiveness has become an research object increasingly. The effect of double-layer mixed material’s absorbing coatings on electromagnetic shielding fabrics has not been clarified currently. At the same time, it is difficult to satisfy the broadband requirement for a single type of absorption layer. Carbon nanotubes, graphene, ferrite and nano-nickel powder are used in this paper. Which made it content at 15%, 25% and 35% respectively. The shielding effectiveness test of the stainless steel electromagnetic shielding fabric coating was carried out by the DR-SO4 electromagnetic shielding test system. Through the experiment, some findings are summarized as followed. Regardless of the same mixed materials, different content of shielding effectiveness comparison experiments, or the comparison of the performance of different kinds of materials mixed with the same content of screen combination, when the content is 15%, the best shielding effectiveness is the double-layer combination of Graphene + Ferrite and Graphene + Nickel. Which peak value is 68 dB respectively. In the analysis of the influence factors of the test coating, the larger the thickness and the corresponding resistance value smaller, the higher the combined shielding effect value. The optimal combination order of shielding effectiveness is: reflective layer + absorbing layer + absorbing layer + reflective layer. This paper revealed the influence of double-layer hybrid coating on the shielding effectiveness of electromagnetic shielding fabrics. It has important academic significance for the design, production and evaluation of high performance electromagnetic shielding fabrics.

Research on Shielding Effectiveness Test of Bulkhead in a Compartment Shelter

Electromagnetic shielding effectiveness (SE) measurement method for electronic equipment shelters is specified in the standards. However, the SE measurement of the bulkhead for the compartment type of shelters may be influenced by the shelter panel as the test position is close to the shelter panel, which will lead to undesirable results in some cases, especially in some low-frequency magnetic field tests. In this letter, several reference measurement models for the SE measurement of the compartment type of shelters are proposed. The proposed models are analyzed and compared with the standard tests. Measurements are set up to demonstrate our models, and acceptable results are obtained. The measurement method proposed in this letter is proved to be a more useful way for the compartment type of shelters.

Processing techniques and properties of metal/polyester composite plain material: Electromagnetic shielding effectiveness and far-infrared emissivity

In this study, a composite plain material is composed of woven fabrics containing metal wire with shielding ability and polyester filament that can provide flexibility and far-infrared emissivity. Furthermore, a wrapping process is used to form metal/far-infrared–polyester wrapped yarns, which are then made into metal/far-infrared–polyester woven fabrics. The effects of using stainless steel wire, Cu (copper) wire, or Ni–Cu (nickel-coated copper) wire on the wrapped yarns and woven fabrics are examined in terms of tensile properties, electrical properties, and electromagnetic shielding effectiveness. Moreover, SS+Cu+Ni-Cu woven fabrics have maximum tensile strength, while SS+Ni-Cu woven fabrics have the maximum elongation and SS+Cu+Ni-Cu woven fabrics have the lowest surface resistivity. Stainless steel composite woven fabrics have far-infrared emissivity of 0.89 when they are composed of double layers. electromagnetic shielding effectiveness test results indicate that changing the number of lamination layers and lamination angle has a positive influence on electromagnetic shielding effectiveness of woven fabrics. In particular, SS+Cu+Ni-Cu woven fabrics exhibit electromagnetic shielding effectiveness of −50 dB at a frequency of 2000–3000 MHz when they are laminated with three layers at 90°.

電界・磁界シールド効果測定器(KEC法)の集中定数等価回路

電界・磁界シールド効果測定器(KEC法)の集中定数等価回路

The importance of the electrical contact between specimen and testing fixture in evaluating the electromagnetic interference shielding effectiveness of carbon materials

The quality of the electrical contact between the specimen and electromagnetic interference (EMI) shielding testing fixture (coaxial cable method) is found to be critical to shielding effectiveness testing. The carbon fiber (CF) mat (0.15–0.42 mm thick) and carbon nanofiber (CNF) fiber mat (4.4–4.6 mm thick) are similar in the shielding effectiveness (68–70 dB), but the former is much superior in the effectiveness per unit thickness (200 vs. 15 dB/mm), due to the clinginess of the CF mat (resulting from short fiber protrusion) promoting good electrical contact, even at zero specimen-fixture fastening torque. Flexible graphite (0.13–0.38 mm thick) is superior to CF/CNF mats in both the shielding effectiveness (110 dB) and shielding effectiveness per unit thickness (560 dB/mm), partly due to its deformability promoting the electrical contact. For the CF mat, the shielding effectiveness decreases monotonically with increasing fastening torque, due to the increase in the degree of in-plane fiber preferred orientation and the consequent degradation of the electrical contact between the specimen and testing fixture. In contrast, for both CNF mat and flexible graphite, the torque enhances the shielding. The absorption loss per unit thickness reaches 165, 14 and 500 dB/mm for CF mat, CNF mat and flexible graphite, respectively.

材料屏蔽效能测试方法比较研究

屏蔽效能是对屏蔽体隔离或限制电磁波的能力的度量，是反映屏蔽材料最主要的指标，因此，屏蔽效能测试技术的规范性、适用性至关重要。目前屏蔽效能测试标准已有十几种，包括国标、国军标、行标等，虽然每种方法都能获得实验数据，但不同测试条件下的实验数据差异性很大，影响到屏蔽材料的应用。该文从屏蔽效能测试基本原理入手，分析了现行标准中材料屏蔽效能的主要测试方法，并通过平面屏蔽材料试验验证，对比了GB/T 12190-2006和GB/T 30142-2013中屏蔽室窗口测试法的差异性，进一步试验了不同天线测试距离和校准参考方式对测试结果的影响，以期为屏蔽材料的设计和装备整体规划提供一定的指导。 Shielding effectiveness, a measure of the ability of a shield to isolate or limit electromagnetic waves, is the main indicator of shielding materials. Therefore, standardizing and appropriately applying shielding effectiveness testing techniques occupy a very influential position. Nowadays, there are dozens of standards for shielding effectiveness testing here, including national standard, national military standard, industry standard, etc. Although the experimental data could be obtained by all of these methods, they are quite different under different test conditions, which hinder the application of shielding materials. Based on the basic principle of measurements of shielding effectiveness, this paper analyzes the main measurements of shielding effectiveness of materials by current standards. Through the verification of test of flat screen materials, it compares the differences of shielding enclosure measurements between GB/T 12190-2006 and GB/T 30142-2013. Further, various antenna testing distances and calibration references are tested to provide some guidance for shielding material design and equipment integrated planning.

Setup for EMI Shielding Effectiveness Tests of Electrically Conductive Polymer Composites at Frequencies up to 3.0 GHz

Conductive polymer composites have been receiving increased interest both from the scientific community and industry with a special focus on electromagnetic interference (EMI) shielding applications. In this paper, we present the design, EM wave simulation, and validation through S-parameters measurements of an EMI shielding effectiveness (SE) tester based on the ASTM D4935 standard, to be used in the development of such materials. EM wave simulations and computer aided design were used in parallel to improve the SE test setup performance, which resulted in a unique low-loss coaxial–spherical–conical smooth transition design that ensured the best tradeoff between sample size and performance. The proposed SE tester has an insertion loss smaller than 1 dB, with good reproducibility and a setup-independent frequency response in the frequency range from a few kHz up to 3 GHz.

Studies on electroless nickel polyalloy coatings over carbon fibers/CFRP composites

Interest in electroless plating of nickel based alloys over carbon fibers has increased due to its excellent electrical properties and also due to its corrosion, wear and thermal resistances. In the present investigation electroless nickel based polyalloys such as Ni-P, Ni-Cu-P and Ni-W-Cu-P coatings were deposited over carbon fibers using alkaline citrate based bath. EDX analysis revealed that P content in binary Ni-P was 8.84 wt.%. Incorporation of Cu resulted in a ternary Ni-Cu-P deposit with 15.4 wt.% Cu and 5.6 wt.% P while the incorporation of W together with Cu resulted in a quaternary Ni-W-Cu-P deposit with 3.18 wt.% P, 2.23 wt.% Cu and 2.61 wt.% W. SEM studies showed a smooth nodular free ternary Ni-Cu-P deposit surface, whereas coarse nodules existed for Ni-W-Cu-P deposit. XRD patterns showed Ni (111) as the prominent peak for all deposits. The presence of a Ni (200) and C (110) peaks were also seen for Ni-W-Cu-P deposit. The quaternary Ni-W-Cu-P deposit exhibited marginally a sharper peak, indicating microcrystalline nature of the coating. DSC thermograms showed a single exothermic peak at 365 °C for Ni-P deposit and at 377 °C for Ni-Cu-P deposit. The thermal stability of the coating had increased due to the incorporation of tungsten and copper which is indicated by the shift in exothermic peak to higher temperature (440 °C). Tensile test data revealed that both Ni-Cu-P (580 MPa) and Ni-W-Cu-P (538.8 MPa) deposits showed a decrease in tensile strength as compared to the binary Ni-P deposit (1402.3 MPa). From the electrical resistivity measurements, the ternary deposit showed almost 96% decrease in the resistivity as compared to the uncoated fibers. To characterize EMI shielding effectiveness of the electroless nickel alloys, coatings were made on CFRP composites. It was found from the EMI shielding effectiveness tests that the quaternary deposit exhibited highest shielding effectiveness of 37 dB compared to others, which is well suited for absorption based applications especially in defense sectors.

Conductive cotton prepared by polyaniline in situ polymerization using laccase.

The high-redox-potential catalyst laccase, isolated from Aspergillus, was first used as a biocatalyst in the oxidative polymerization of water-soluble conductive polyaniline, and then conductive cotton was prepared by in situ polymerization under the same conditions. The polymerization of aniline was performed in a water dispersion of sodium dodecylbenzenesulfonate (SDBS) micellar solution with atmospheric oxygen serving as the oxidizing agent. This method is ecologically clean and permits a greater degree of control over the kinetics of the reaction. The conditions for polyaniline synthesis were optimized. Characterizations of the conducting polyaniline and cotton were carried out using Fourier transform infrared spectroscopy, UV-vis spectroscopy, cyclic voltammetry, the fabric induction electrostatic tester, and the far-field EMC shielding effectiveness test fixture.

Alternative Antenna Research to Optimize MIL-STD-188-125-1 Standard Shielding Effectiveness Measurement

Currently, When Shielding effectiveness(SE) test was conducted in MIL-STD-188-125-1, The experiments are using Loop antenna, Log Periodic(LP) antenna, Biconical antenna about shielding in the frequency range of 10k∼1GHz. But, Their size in the shielding effectiveness test influences chamber construction costs. And these influences play a role in increased production costs. So spiral antenna to clear antenna size problem was proposed. This antenna has small size and function to cover broad frequency compared to other antennas. To evaluate antenna performance, we use commercial software simulation program. And we observe radiation characteristic changing arm width and distance between arm. First, through magnitude analysis of S-parameter, antenna characteristic according to each arm distance is analyzed. Secondly, through Theta/Degree Vs. dB function and 2D/3D model, radiation pattern of antenna is investigated. Third, radiation energy magnitude and characteristic of antenna is investigated in simulation program.

Shielding effectiveness testing method of pulse electric field based on GTEM cell

In order to evaluate the shielding ability of materials under the radiation of electromagnetic pulse (EMP), a test method based on GTEM cell is put forward. And the test theory and the components of test system are introduced. The shielding box method is verified to be reasonable with simulation. The shielding effectiveness (SE) of one material is tested with this method, and the test results are compared with the results based on the coaxial method. The results show this test method can be used to test the effect of SE on EMP, and the test results can reflect the true shielding ability of the test material.

Characterization of an injection-moulded car audio chassis made of polycarbonate–(acrylonitrile–butadiene–styrene)-based composite using metal-coated carbon fibre

Engineering plastics are widely used as a substitute for stainless steel in the automobile industry to reduce weight and to improve fuel efficiency. In this paper, a polycarbonate–(acrylonitrile–butadiene–styrene)-based composite with nickel-coated carbon fibre was developed, and the application of the composite to a lightweight car audio chassis was examined. The mechanical and electrical properties of the composite were evaluated through various physical tests, i.e. tensile, impact, flexural and electromagnetic interference shielding effectiveness tests. In addition, the characteristics of this material were compared with those of a material previously developed by the present authors, i.e. a polycarbonate–(acrylonitrile–butadiene–styrene)-based composite with metal fibre and glass fibre. Finally, the actual car audio chassis was made by injection moulding under various moulding conditions pertaining to the injection speed and the tool temperature to find the optimum injection-moulding conditions. Two required key tests, i.e. a full-scale electromagnetic interference shielding effectiveness test and vibration analysis, were conducted to confirm the applicability of the polycarbonate–(acrylonitrile–butadiene–styrene)-based composite with nickel-coated carbon fibre as a material for a car audio chassis.