The Frequencr Response Characteristics Of The Frequencr Selective Fabrics With Periodical Structure Made Of U-Shaped Stainless Steel Yarn Velvet

At present,many periodic structures with frequency selective characteristic are prepared,whose structural units are metal materials.There are some problems,such as hard material,heavy weight,complicated and difficult preparation process and so on.The conventional textile materials are these materials where electromagnetic waves can be transmitted,which have little influence on the propagation of electromagnetic waves.With the rapid development of textile technology,the preparation technology of metal fiber and textile processing technology are becoming more and more sophisticated,making it possible to fabricate three-dimensional periodic structure fabric with electromagnetic function.Compared with planar frequency selective fabric(2D FSF),three dimensional frequency selective fabric(3D FSF)can be designed for more sizes.3D FSF has more design dimensions and smaller unit size.Compared with the common three dimensional frequency selective surface(3D FSS)made by metal material,3D FSF is lighter,more convenient and flexible.In the paper,through the textile technology of tufted carpet processing,3D FSF velvet carpet samples with both of frequency selection characteristics and light and soft properties were prepared.Stainless steel / cotton blended yarns were used as conductive materials.Ordinary yarns or fabrics were used as dielectric materials.The multiscale structure of 3D FSF was analyzed.The influences of the conductive yarn,the structure and size of the periodic unit,and the preparation methods on the frequency response characteristics were systematically explored.Finally,through the modeling and simulation of HFSS software,the feasibility of U 3D FSF made by velvet was verified.The main contents are as follows.(1)Study on the multiscale structure and characteristics of 3D FSF.The multiscale structure of 3D FSF was proposed,which included conductive yarn(CY),essential conductive structure unit(CFSU),periodic conductive structure unit(PCSU),periodic structure unit(PSU)and 3D FSF.Electromagnetic parameters would affect the frequency response characteristics,such as the fineness of CY,the content of metal fiber,the structure of CFSU,the shape and length of PCSU,and so on.(2)Study on frequency response characteristics of 3D FSF based on the multiscale structure.The model samples were prepared by hand.The carpet samples were prepared by the electric carpet fabricated gun and the Wilton carpet loom.The parameters affecting the frequency response characteristics of samples were studied.The following conclusions were drawn.The more the content of stainless steel or the greater the fineness of the yarn,the more obvious the resonance of the sample is.The higher the content of the stainless steel or the greater the fineness of the yarn,the more obvious the resonance phenomenon of the sample is.The resonance frequency of the U-shaped velvet samples is close to that of looped pile samples with the same size.The increase in the distance of loop pile b leads to the increase of the resonant bandwidth of the cashmere sample.With the increase of the length of PCSU,the resonant frequency decreases and the half peak width of the resonant peak becomes larger.The less the number of U or loop piles in PCSU,the more obvious the resonance phenomenon is.3D FSFs with the same PCSU size and different PCSU types have different resonance phenomena.The Wilton carpet fabrics with frequency response characteristics include the upper and the lower.The resonance phenomenon of the upper carpet is not obvious.The lower carpet has a certain hindrance to the propagation of electromagnetic waves and resonates in some frequency bands.The random inclination of the villi has little influence on the frequency response characteristics of the 3D FSF prepared by the Wilton loom.(3)Research on 3D modeling and Simulation of 3D FSF.Through the electromagnetic simulation software HFSS,the geometric model of U-shaped velvet sample was set up.The influences of the electromagnetic parameters and structure dimensions on the frequency response characteristics were analyzed.The results obtained from the simulation results are similar to those in physical samples.A simple structure of PCSU is simplified into a geometric model,which makes small errors in simulation.In the process of modeling and simulation,the error of simplifying the complex PCSU to simple geometric model is large.