Research Of Integrated Absorbing And Relfection Mechanism In The Electromagnetic Shielding Composite Material

Electromagnetic technology is a double-edged sword, it brings us muchconvenience. However, the popularity of high-power electrical equipment also causessome safety and environment problems such as electromagnetic interference,electromagnetic leaks and electromagnetic pollution. The traditional shieldingmaterial and way of shielding cannot meet the complex requirements in the newelectromagnetic environment especially when the intensity of electromagneticradiation increases. So to research and prepare a new kind of "green" material whichhas a higher shielding effectiveness and can cope with a wider frequency but with alower density becomes a "hot spot" in the material science.In this paper, we integrate the reflection layer and the absorbing layer as one.Comparing with any other material, this kind of material can reach a high shieldingeffectiveness but maintain a low density. As we all know, although traditionalshielding material can reach a high electromagnetic shielding effectiveness at present,the main shielding mechanism is reflection. That is to say, those material are onlyrestricting the energy into the very area, but not convert them into other kind ofenergy. So the result is, it causes a new electromagnetic interference at other place. Insome cases, it can cause resonance, making big trouble to the operation of equipment.However, the integrated material can remedy the defect of traditional material—itnot only absorbs the interfering radiation and broadens the band, but also maintains ahigh shielding effectiveness like traditional material.With the help of fiber reinforced resin process method, the experimentsuccessfully finished the preparation, and this material not only had functionalfeatures, but also had some structured features. Four-point probe, scanning electronmicroscopy and vector network analyzer were used to analyze the material. At thesame time, broadband coaxial, microwave anechoic chamber methods were used totest its electromagnetic properties. The mechanical properties of material were also beanalyzed. With the help of theoretical model and metrical value, the paper researchedthe relationship between conductivity and shielding effectiveness, and described themechanism of wave absorbing when the absorbent feature, content and material sizewere shifting. The paper at last found the best parameters of the integrated material; itcould promote electromagnetic wave absorbing ability as well as the efficiency ofband coverage.The research indicates that, Aluminized glass fiber's length and adding contentwere important to the conductivity. Material would change into a conductor whenfiber content above15%. It could keep a stable shielding effectiveness when fiber content reached40%to60%. However, excessive fiber content would result in thedeclination of the shielding effectiveness. The paper also found that, because of theco-work of average contact point and technological factors,4cm~10cm fiber lengthcould more possibly gain a higher SE. The paper also gave some explanation on therelationship between technological factors and shielding, it believed that the layerstructure of material had some positive effect on shielding, and calculated theinductive losses. The research confirmed that it was wrong to add insulated glass fiberand black carbon into the material.Bringing absorbing layer into material was a feature of the paper. Through themethod of composite and superposition the W-type ferrite and other absorbent, thepaper researched the relationship between material parameters and absorbing rate.Absorbing rate of multiple phase composite material was better than single phasematerial, and it was helpful to decrease the matching thickness and increase theabsorbing rate when the alloy powder content was25%. This paper also researchedthe absorbing ability of multiple layer material, and found that the choice of absorbentand the sequence of layer were important to the absorbing rate. The research showthat, matching thickness would decrease and absorbing rate would increase when weput the bigger dielectric constant layer in the inside and put the lower dielectricconstant layer on the outside.The paper discussed relationship between shielding effectiveness and clutterrestriction effectiveness in detail. Metrical and calculated value shows that the usageof clutter restriction layer could hardly increase the total shielding effectiveness,however, it could efficiently restrict the clutter and broaden response band. The papercalculated the ability of material restricting clutter in a vertical interference situation,and obtained that, the integrated material could restrict60%clutter from5GHz to18GHz area, and its restriction rate could be higher at the high frequency area.At last, the paper analyzed mechanical properties of material, and its bending andtensile strength were tested. The process of stress redistribution and wreck mechanismwere analyzed with the relationship of Aluminized glass fiber. The paper pointed outthat, comparing with other kind of material, such kind of material could used into theplace which baring bending stress more than tensile stress.