| Metal fiber electromagnetic shielding(EM) fabric is light and soft, comfortable and durable, its shielding performance is good and its structure is controllable. It has been the first choice for the lightweight and flexible shielding materials. However, the most of qualitative researches paid attention on specific fabric varieties and many complex fabric parameters, and was lack of effective extraction on shielding effectiveness influence factors.This paper analyzes the structure of metal fiber yarn fabric, puts forward that the effective electromagnetic shielding structure of this kind of fabric is only made of metal fiber yarn in the fabric. The different bare copper wire models of the EM fabric were established. They are one-way parallel models, two-way vertical cross node models, two vertical cross with node disjoint models, surrounded by connecting or not connecting models, ground or not ground models. Further, above typical models made of stainless steel filament, stainless steel fiber blended yarn, stainless steel filament core spun yarn, silver plated filament, stainless steel filament twisted yam were prepared. In order to verify the accuracy of the model results, some fabric samples with stainless steel blended yarn and core spun yarn were woven in different metal yarn arrangements. The SE and reflective factor in1-18GHz of the metal yarn models and the fabric samples were tested by EM room method. The results were compared and analyzed. Finally, the EM shielding mechanism of the stainless steel (SS) and silver fiber fabrics were analysed, and FORTRAN Programming based on metal mesh shielding effectiveness calculation formula was made, the simulated and measured values were analyzed.The results show that, the distance between adjacent metal fiber yarns is the key factor affecting the SE, and SE evaluation simply by fiber content, fabric density and tightness is not suitalbe. In a certain range, the smaller the distance is, the better the SE is. The SE of one-way arrangement and two-way arranagement sample is the same, however the one-way arrangement sample has obvious directivity. Under the experimental conditions, the metal conduction at the cross point has little effect on SE, which still needs further study. The EM wave is transverse electric wave in EM room method, and the SE and reflective factor of the samples are obvious affected by the incident direction of the EM wave, and metal yarn grid shape would affect the SE of the fabrics. With the vertical spacing increased, the SE and the reflection coefficient decreases. Variation of transverse spacing has no effect on SE and the reflection coefficient. The SE of horizontal parallel sample with the longitudinal spacing b and the SE of thegrid sample with the vertical spacing b and arbitrary lateral spacing are the same.The EM shielding fabrics with different materials and different spinning methods have great influence on SE. When the other conditions are the same, the SE of the SS blended yarn is the best and the SE of the fabrics respectively made of SS filaments and SS covering yarn and SS ply yarn is the same. The SE of samples only made of SS fibers after corrosion is not better than that of the original cotton/SS covering yarn samples.The absorptive, reflectivity and transmissivity of SS fabric and silver plated fabric were calculated, the results show that, the SE of the SS fabric and silver plated fabric mainly depends on the reflection. The analog value and the measured value of the SE have a certain bias, which have confirmed the existence of differences in the metal plate and textile containing metal fibers, on the other hand, the simulation results also verify the test frequency and the pitch has a significant impact on the shielding effectiveness. |
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