Development Of Isotropic Flexible Absorbing Fabric

Electromagnetic wave absorbing materials can effectively reduce the signal characteristics of electric and magnetic signals of specific targets,and reduce their low detectability.They are widely used in equipment and key target stealth camouflage,information equipment to prevent electromagnetic hazards,electromagnetic information leakage prevention and so on.The flexible absorbing material can overcome the common problems of the current absorbing material,such as large thickness,high density,single product function,and most materials are rigid.It is widely used in electromagnetic wave protective clothing and electromagnetic equipment anti-jamming awning materials in special environments.Greatly expand the application field of absorbing materials.At present,the absorbing materials have the anisotropy of the transverse and longitudinal directions of the material,and different incident wave angles significantly affect the absorbing effect of the fabric,which limits the application of the absorbing fabric.Based on the design principles of absorbing materials,this thesis starts with the development of isotropic absorbing fabrics,and studies the development techniques of three kinds of fabrics:absorbing coated fabric,absorbing tufted blanket fabric and absorbing non-woven fabric.The influence of material properties on the type of absorbing agent,yarn structure and fabric structure was analyzed.The theory and process parameters of textile processing suitable for isotropic absorbing fabric were established.The details are as follows:The first part of the development of absorbing coated fabrics,by changing the ratio of nickel,iron powder ratio,coating agent to nickel iron powder ratio,coating thickness and other process conditions,designed 30 different specifications of fabrics,and tested the thickness of the fabric,Gravity and reflectivity.After data analysis,the absorbing properties of fabrics are isotropic in the frequency range of 12 GHz to 18 GHz,and the best absorbing performance is nickel and iron powder ratio of 85:15.The ratio of coating agent to ferronickel powder is 1:1.5,the coating thickness is 1 mm.When the reflectance is lower than-10 d B,the percentage of reflectance is less than 10%,the percentage of absorptance is greater than 90%,and the width of the fabric having a reflectance of less than-10 d B is 5 GHz.The second part of the development of the absorbing wave tufted blanket fabric,12different kinds of tufted blanket fabrics were designed by changing the number of stitches within 10cm,the number of single needle feeding yarns,and the height of hairiness.The gram weight and reflectivity of the fabric were tested.After data analysis,the absorbing properties of the fabric were isotropy in the frequency range of 12 GHz to 18 GHz.The best absorbing performance was 2.5 cm for the feather height and the number of yarns fed by a single needle is 15,the number of stitches within 10 cm is 22 steps.The fabric has a reflectivity of less than-10 d B in the frequency range of 12 GHz to 18 GHz,a bandwidth of 6 GHz,and a reflectivity of less than-20 d B and a bandwidth of 3 GHz even in the two frequency bands of 12 GHz-14 GHz and 17 GHz-18 GHz.The third part of the development of absorbing non-woven fabrics,by changing the content of metal fiber,needle density,metal fiber types and other process conditions,designed 30 different specifications of non-woven fabrics.The thickness,gram strength,breaking strength,elongation at break,air permeability and reflectivity of the fabric were tested.After analysis of the data,it can be concluded that in the frequency band of 12 GHz to 18GHz,the absorption performance of the fabric is isotropic.The best absorbing performance is a fabric with stainless steel fibers with a needle density of 500 needles/cm~2and a stainless steel fiber content of 30%.The fabric has a reflectance of less than-10 d B and a bandwidth of 6 GHz in the frequency range of 12 GHz to 18 GHz.Even in the frequency range 14 GHz-18 GHz,the reflectivity is lower than-20 d B and the bandwidth is 4 GHz.The fabric containing nickel-iron fibers has a needle density of 500 needles/cm~2and a nickel-iron fiber content of 10%.The fabric has a reflectance of less than-10 d B and a bandwidth of 6 GHz in the frequency range of 12 GHz to 18 GHz.Even in the frequency range of 14 GHz-18 GHz,the reflectivity is lower than-20 d B and the bandwidth is 4GHz.