The Preparation And Electromagnetic Shielding Behavior Of Frequency Selective Fabrics

Frequency selective surface（FSS）can traverse or obstruct electromagnetic wave in a particular frequency,which is widely used in antenna and radar applications.However,the materials made on traditional FSS are composite materials or rigid materials,and the most of methods are etching,printed circuit board so that can’t be wearable smart fabric due to heavy weight and not soft.Therefore,this paper focuses on combining soft textile with conductive materials to make frequency selective fabric（FSF）obtaining the characteristic of flexible wearable,sensing and electric heating.The specific research works as follows:（1）The mechanism of different structures to frequency selection performance was studied.Due to the influence of different periodic arrangement structures to frequency selective electromagnetic shielding,the equivalent circuit model is used to analyze the basic periodic structure units,which are mainly classified into L&C in series and L&C in parallel two types.A complex structure is decoupled by the periodic structure units,and the corresponding peak value of complex structure is fitted by the structure units.（2）The FSF was prepared in four technologies of different processes.FSF prepared by the metal patch plate obtained a better SE_max reached 63 d B.Using silver-plated nylon and stainless-steel yarn as metal materials,the FSF with periodic structures were prepared by embroidery technology to obtain electromagnetic SE（24 d B）.FSF prepared by impregnation method by using self-made Ag NWs conductive materials led to SE_max attained to 32 d B;Using metal yarns and polyester yarns as raw materials,the FSF was prepared by clipping and carving technology and SE_max reached to 57 d B.（3）The influence of different processes to frequency selective electromagnetic shielding was investigated.The results showed the embroidered fabric#16 had a SE peak（24.1 d B）at 1330 MHz.The SE peak value of SG structure prepared by impregnation method reached 32 d B.To further improve production efficiency,adopting the weaving technology to made FSF.The SE peaks of Ss fabrics W:D of2.5:0.5,5:1 and 6:1.5 are 57.2 d B,55.4 d B and 35.1 d B,respectively.It can be concluded that good frequency selective electromagnetic SE can be obtained by using embroidery,impregnation and weaving techniques.（4）A hot-pressing process was proposed to enhance the firmness of Ag NWs on PET fabrics.The results showed that the conductivity of hot pressing Ag NWs/PET fabrics（HF）was 464.2 S/m and the without hot pressing Ag NWs/PET fabrics（NF）was94.9 S/m.After 5 adhesive tape cycles,the conductivity of HF was maintained at about32 S/m,while NF is almost non-existent conductivity.Besides,the washed HF possessed the properties of strain sensing（ΔR/R₀ arrived to-14%）and electric heating（temperature reached 110℃when the current is 0.08 A）.Therefore,hot pressing technology can improve the conductive,durable and wash,and HF has the potential as a multi-functional wearable fabric.In this paper,the technologies of patch,embroidery,impregnation and weaving were used to prepare FSFs.According to analyzing and decoupling the periodic basic units,the different processes influence on the frequency selective electromagnetic shielding characteristics was researched,and the problem of the conductive materials easily shedding by impregnation method was solved.