Simulation Of Electromagnetic Wave Propagation In Knitted Fabrics And Research On Shielding Performance

Electromagnetic textiles have become an important part of high performance functional materials and have been widely used.But the research and development cycle of electromagnetic textiles is long and the cost is high.Therefore,it is very important to study the propagation law of electromagnetic wave in fabric and to design electromagnetic shielding fabric digitally.The purpose of this research is to realize the electromagnetic simulation of knitted fabric's three-dimensional structure,and to simulate and calculate the influence of the electromagnetic parameters of fabric model on the electromagnetic shielding performance.A solution to improve the electromagnetic shielding performance of knitted fabric is put forward:inserting axial yarn with electromagnetic function in the warp and weft direction of the knitted fabric.Firstly,construct knitting mesh structure with conductive composite yarn,silver-plated yarn and conductive stainless steel yarn,knit weft weave structure by using blended yarn of stainless steel fiber with different conductive properties,and the electromagnetic shielding efficiency of the materials were tested by vector network analyzer.The results show that knitted fabric with net structure has good shielding effect.The electromagnetic shielding efficiency of pure conductive loss meshes(using conductive composite yarn and conductive stainless steel yarn as material)varies linearly with the increase of frequency in the measurement frequency range of 10 MHz-3 GHz.The double bead mesh fabric has the best shielding efficiency in the range of 10 MHz-3 GHz frequency measurement,and the thickness of the material has a significant effect on the electromagnetic shielding effect in the low electromagnetic frequency range.Secondly,the micro model of knitted f'abric is constructed based on the structure and size of 1+1 rib structure.And then the uniaxial,biaxial and triaxial fabric structure of 1+1 rib structure are constructed in order to achieve simulation.Finally,the simulation model of electromagnetic shielding knitted fabric is established,and the propagation of electromagnetic wave in knitted fabric is simulated by finite integral method.The effects of electromagnetic parameters,fabric structure,incidence angle of electromagnetic wave and the axial yarn properties and layers of knitted fabrics were analyzed.The results show that the shielding efficiency of knitted fabric increases significantly with the increase of the conductivity of the material,and when the conductivity is greater than 300 S/m,the apparent dispersion is observed,and the surface current density of the fabric is polarized with the increase of the incidence angle of the electromagnetic wave.Under the action of electromagnetic wave,the electromagnetic shielding fabric with conductive loss produces inductive current,the direction of the inductive current is consistent with the direction of electric field,the intensity of electric field is obviously affected by the frequency of electromagnetic wave.The direction of magnetic field is perpendicular to the direction of electric field and the intensity of magnetic field is affected unconspicuously by the frequency of electromagnetic wave.The lining of the axial electromagnetic yarn can effectively improve the electromagnetic shielding performance of the fabric.In the multi-layer axial weft knitted fabric,the surface conductive layer plays a major role in the reflection loss of the electromagnetic wave,and with the number of layers of the axial conductive yarn increasing,the more obvious the reflection loss of electromagnetic wave in fabric is,the better the shielding effect of three layers of axial conductive fabric is.