Electromagnetic Shielding Effectiveness Of Fabrics Research Articles

FDTD Numerical Calculation of Shielding Effectiveness of Electromagnetic Shielding Fabric Based on Warp and Weft Weave Points

In this article, the finite-difference time-domain (FDTD) method is used to study the scientific numerical calculation method of the shielding effectiveness (SE) of the electromagnetic shielding (EMS) fabrics. First, the fabric is divided into overlapping region, longitudinal single yarn region, transverse single yarn region, and interstice region of the warp (weft) weave points according to the yarn arrangement characteristics of the warp and weft weave points. Then, a structure model of the fabric is established based on the warp and weft weave points and the fabric weave. The partition coefficient and discrete method of Yee's grid is determined. The electromagnetic parameters of the grid are measured by the coaxial transmission/reflection method, and the appropriate absorption boundary conditions, excitation sources, and constraints are set to establish the physical model of the fabric. Finally, the physical model is numerically calculated to obtain the SE using EastFDTD electromagnetic calculation software. The contrastive analysis of the numerical simulation and the measured data is made combining the theory. The accuracy of the numerical simulation results, the correction method of the discrete factor, and the reason of the error are discussed. It is concluded that the model has been satisfied with the numerical calculation of the SE of the EMS fabric.

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.

Evaluation of electromagnetic shielding effectiveness of fabrics produced from yarns containing metal wire with a mobile based measurement system

Evaluation of electromagnetic shielding effectiveness of fabrics produced from yarns containing metal wire with a mobile based measurement system

A calculating method for the electromagnetic shielding effectiveness of metal fiber blended fabric

In order to obtain a simple and accurate calculation method of shielding effectiveness for woven fabric containing metal fiber yarns, a conductive grid structure model composed of two parallel metal yarn periodic arrays was established. The two periodic arrays were cross-arrangement. The calculation formula of shielding effectiveness for the fabric was deduced through the transfer matrix of the electromagnetic field. The theoretical value of shielding effectiveness of the fabric using the theoretical formula and the measured value tested by the shielding chamber method were compared. Both sets of data were analyzed respectively from the metallic yarn periodic spacing, diameter, electric conductivity, electromagnetic wave polarization direction, and the weaving angle. The result shows that a reasonable agreement between the theoretical value and the measured value has been achieved in a frequency range from 4 to 14 GHz. This shows that the theoretical calculation model is simple, highly precise, and is valuable for the design and development of fabric containing metal fiber yarns. It can be used for estimating the electromagnetic shielding effectiveness of the fabric.

FDTD computation of shielding effectiveness of electromagnetic shielding fabric based on weave region

Numerical computation of shielding effectiveness (SE) of electromagnetic shielding fabric (EMSF) is a research difficulty, making no a suitable model for it at present. This paper proposes a partition method based on the yarn diameter and fabric weave structure. The fabric is divided into overlapping region, lateral single yarn region, longitudinal single yarn region, and interstice region according to the weave feature. A fabric structure model for FDTD numerical computation of the SE is constructed. The electromagnetic parameters of each region are tested according to the transmission and reflection method. The Yee’s grid discretization method of the structure model is given, and the absorption boundary and the excitation parameters are set to determine the physical model of the fabric. The numerical computation of the physical model is done by the East FDTD electromagnetic computation software. The computation data are compared with the actual testing data, and the results show that the computation results of the SE of the EMSF with the proposed model are satisfied. The research in this paper provides an important reference value for the design, production, evaluation, and theoretical study of the EMSF.

Polypyrrole/barium titanate/poly(acrylonitrile-co-methylacrylate)–deposited cotton fabrics: Electromagnetic shielding

In this study, polypyrrole was deposited separately on barium titanate, barium titanate-poly (acrylonitrile-co-methylacrylate) nanocomposite-coated textile fabrics by an in-situ chemical polymerization process. Electromagnetic shielding effectiveness, electrical conductivity, chemical structure, and morphology of fabrics were fully characterized and systematically studied for investigation of individual effects of barium titanate, pyrrole polymer, and barium titanate-poly (acrylonitrile-co-methylacrylate) on obtained fabrics’ conductivity and shielding behaviour. Electromagnetic shielding effectiveness of the fabrics was determined according to the ASTM D4935-10 protocol, by using a coaxial transmission line measurement technique in the frequency range of 15–3000 MHz. Electrical characteristics were measured by the two-end method. Electromagnetic shielding effectiveness data suggested that polypyrrole-coated fabrics had better electromagnetic shielding effectiveness than polypyrrole-barium titanate and barium titanate-poly (acrylonitrile-co-methylacrylate)-coated fabrics. On the other hand, conductivity increased due to the interaction between polypyrrole and barium titanate-poly (acrylonitrile-co-methylacrylate), with fabric conductivity values also increased with the use of barium titanate. Spectroscopic characterizations of coated fabrics were determined using Fourier transform infrared spectroscopy. Analyses demonstrated that there is a strong interaction between cotton and polypyrrole and barium titanate, and also with poly (acrylonitrile-co-methylacrylate)-barium titanate. Morphological characterizations of the coated fabrics were examined by scanning electron microscopy. Colour measurements of fabric samples were performed for determination of colour intensity as a function of polymerization efficiency.

Electromagnetic Shielding Effectiveness and Manufacture Technique of Functional Metal Composite Knitted Fabrics

In order to fabricate fabrics with electromagnetic shielding effectiveness (EMSE) and other function, we fabricated Crisscross-section polyester /antibacterial nylon / stainless steel wires (CSP/AN/SSW) composite yarns with stainless wires as core yarn, antibacterial nylon and crisscross-section polyester as inner and out wrapped yarns, respectively. Knitted fabrics were fabricated with the metal composite yarns with wrap amount of 8 turns/cm on a circular knitted machine. Furthermore, the EMSE of the metal composite fabrics were evaluated by changing the lamination amounts and lamination angles. The results show that when the lamination amount was four, lamination angles were 0°/45°/90°/-45°, the EMSE of the fabrics reached to-10--20 dB in the frequency range of 300 KHz to 3 GHz.

Electromagnetic interference shielding effectiveness of SS/PET hybrid yarn incorporated woven fabrics

A detailed study of electromagnetic shielding effectiveness (EMSE) of woven fabrics made of polyester and stainless steel/polyester blended conductive yarn was presented in this research work. Fabrics with different structures were analyzed and their shielding behavior was reported under different frequencies. Shielding efficiency of fabric was analyzed by vector network analyzer in the frequency range of 300 kHz to 1.5 GHz using coaxial transmission line holder. The effects of different fabric parameters such as weft density, proportion of conductive weft yarn, proportion of stainless steel content, grid openness, weave pattern and number of fabric layers on EMSE of fabrics were studied. The EMSE of fabric was found to be increased with increase in proportion of conductive yarn in the weft way. With increase in overall stainless-steel content in the fabric, the EMSE of fabric was increased. As such weave is considered, it did not have significant effect on EMSE of fabrics. But fabric with lower openness and aperture ratio showed better conducting network, hence better shielding. With increase in number of layers of fabric and ply yarns, EMSE of fabric was increased.

Electromagnetic shielding effectiveness of copper core-woven fabrics

Copper is selected as a conductive filler to produce copper core yarns to make woven fabric using a network analyser equipment, and the electromagnetic shielding effectiveness of these fabrics is measured in the frequency range of 20–18,000 MHz. With an increase in the number of conductive fabric layers, finer yarn count, warp density, weft density and cover factors, an increase in shielding effectiveness is observed. With an increase in copper wire diameter, a decrease in shielding effectiveness is observed.

Electromagnetic Shielding Effectiveness of Fabrics with Metallized Polyester Filaments

A preliminary study of the electromagnetic shielding effectiveness (EMSE) using metal coating films and a vacuum evaporation deposition technique with the woven fabrics made of metal/PET filaments is presented. Using coaxial transmission equipment, the EMSE of these films and fabrics was measured in the frequency range 2250—2650 MHz. The experimental results indicate that different coating materials have different EMSE, with a thicker coating film having a higher EMSE. In addition, a woven fabric with lower aperture ratio made from metal/polyethylene terephthalate (PET) filaments has higher EMSE, and the electromagnetic shielding of polarized electromagnetic waves possesses orientation effects. The paper provides theoretical guidance for designing flexible electromagnetic shielding products.