Reserch On Preparation Principle Of Flexible Microwave Absorbing Material Basedon Frequency Selecting Surface

A very key principle in the design of radar absorbing materials is that the material must have a good impedance matching,so that the incident electromagnetic wave will not be strongly reflected on the surface of the material,thereby reducing the reflectivity of the material and reducing the probability of the target being detected..At present,the research content on the impedance matching of absorbing materials is mainly in two aspects.On the one hand,the material is matched.The impedance matching is achieved through the mutual matching of electricity and magnetism.This method requires the addition of magnetic particles,and the density of magnetic particles is relatively high,and it will increase the weight of the absorbing material,which does not meet the requirements of lightweight materials.The other aspect is the structure.The current research hotspot in the structure is the introduction of frequency selective surface into the material,mainly through the design of the structure of the frequency selective surface and the design of the material to achieve perfect impedance matching.The traditional metal frequency selective surface also does not meet the requirements of lightweight,and the bandwidth is narrow.The new frequency selective surface made of conductive composite materials has many advantages,that makes it a research hotspot,and they includes light weight,corrosion resistance,and high temperature resistance,etc.And the frequency selective surface made of a conductive composite materials will make the absorption bandwidth of the absorbing material larger.In this paper,the method of Spacial Confining Forced Network Assembly is used to prepare the material of the frequency selective surface(FSS)layer,namely the SCF/PDMS conductive composite material,and then the silicon rubber dielectric layer is loaded on both sides of the FSS layer.The prepared absorbing material has light weight and resistance to The advantages of corrosion and high temperature resistance,and can be achieved in the two frequency bands of K band(18-26.5 GHz)and Ka band(26.5-40 GHz),the absorption bandwidth is 22 GHz with an absorption rate greater than 90%.The main research contents are as follows:(1)Use ANSYS HFSS software to conduct electromagnetic simulation research on absorbing materials.The first is the research and design of the overall structure of the absorbing material,mainly the simulation study of the loading method of the dielectric layer.The results show that:compared with the FSS-DE-M method and the DE-FSS-M method,the DE-FSS-DE-M method has the best absorbing rate and the largest bandwidth,that is,the dielectric layer is distributed in two FSS layers.The material has the best absorption rate when it is sideways.After that,the material properties and geometric parameters of the flexible absorbing material were simulated and the results showed that the unit shape is a ring unit,the unit distance is 7.5 mm,the outer radius of the ring is 3.6 mm,and the inner radius is 1.3 mm.The total thickness of the dielectric layer is 3 mm,the conductivity of the FSS layer is 75 S/m,the dielectric constant of the dielectric layer is 3,and the dielectric loss tangent value is 0.01,which realizes the full band of K and Ka.The absorption bandwidth is 22 GHz with an absorption rate greater than 90%,and the absorption rate is above 96%.(2)In order to improve the flexibility of the absorbing material,the SCF/PDMS conductive composite material,which is the raw material of the FSS layer,is prepared by the method of Spacial Confining Forced Network Assembly(SCFNA).By designing orthogonal experiments,the multiple linear regression equations between the resistance response value of SCF/PDMS conductive composite products and the three factors of carbon fiber content,mixing speed and mixing time are obtained,and the conductivity prediction model is established,and the carbon fiber can be adjusted.Variables such as content,mixing speed and mixing time realize the control of the conductivity of the SCF/PDMS conductive composite material,that is,the controllable adjustment of the conductivity of the FSS layer material.(3)Prepare the FSS ring unit by using a punch and design a positioning mold,and use a doctor blade coater to scrape the film to make the FSS layer and the dielectric layer composite to obtain a complete absorbing material,and test the absorbing performance of the material,The results show that the experimental results are in good agreement with the simulation results.