Characterization For Electromagnetic Shielding Behavior On The Looping-Grid Lattice Structure With Carbon Fibers

Nowadays, reflection is widely used in shielding electromagnetic (EM) radiation, which will cause multiple-pollution. So using absorption-type EM shielding materials which reduce EM radiation by energy dissipation is a more positive and efficient way. Grid lattice period structure EM shielding materials are the typical absorption-type EM shielding material. Due to low density, high intensity, good stability and good electrical conductivity, carbon fibers and their composites have been concerned by public in recent years.The looping-grid structure model is proposed, and put the carbon fiber looping-grid structure compound fabric as the main research object. The effects of structure parameters of looping-grid structure compound fabric on the shielding properties are studied. And the far-field microwave scattering intensity distribution is emphatically analyzed.Through the experiments, the effects of the frequency of radiation source, the height of looping-grid structure, and the spacing between the looping-grid structure and the filaments respectively on the shielding property have been discussed in the microwave range. The experimental results show that:the shielding efficiency (SE) peak values of the looping-grid structure compound fabric focus in the beginning of the measured frequency. The smaller the spacing is, the larger the SE value is. The peak position is affected by the spacing of carbon fiber filaments. For the sample the height is6mm and the spacing is3mm, the SE is high up to40dB.The effects of structure parameters and microwave incident angle have also been discussed on microwave scattering intensity angle distribution. The experimental results show that:the scattering intensity of the samples is anisotropy, affected by the direction of carbon fiber filaments arrangement. Structure parameters and microwave incident angle have different effects on the back scattering and forward scattering. Intensity peaks occur in the direction of specular reflection and transmission. The back scattering relative intensity distribution of the looping-grid structure compound fabric is lower than that of the paralleled arrangement fabric in the whole view angles. In the incident angle of0°and9mm spacing, the back scattering relative intensity of the looping-grid structure compound fabric is21.47%less than that of the paralleled arrangement fabric. There are no differences in forward scattering relative intensity distribution between looping-grid structure compound fabric and paralleled arrangement fabric.There is a linear positive correlation between the average reflectivity and transmittivity of paralleled arrangement fabric and the incident angle. In the certain incident angle, the average reflectivity and transmittivity is nonmonotonous with spacing. When the spacing is6mm, both the average reflectivity and transmittivity is lowest, show that this sample absorbs and shields most EM energy. Take the incident angle of15°for example, the characteristic peaks of the looping-grid structure compound fabric and paralleled arrangement fabric are discussed. The maximum peak of the reflectivity of the looping-grid structure compound fabric is11.42%smaller than that of the paralleled arrangement fabric, but the corresponding peak area is67.83%larger. The scattering intensity of the looping-grid structure compound fabric is weakened in the resonance frequency, scattered to other frequencies, thus widening the resonance peak. The maximum peak position is substantially the same in the transmittivity spectrum of the looping-grid structure compound fabric and paralleled arrangement fabric. The maximum peak of the transmittivity of the looping-grid structure compound fabric is23.43%smaller than that of the paralleled arrangement fabric, and the corresponding peak area is23.07%larger.The experiments make a comparison of the spectrum and the characteristic peaks of the reflectivity and transmittivity of different carbon fiber structure compound fabric in the same carbon fiber content, namely the looping-grid structure compound fabric, the paralleled arrangement fabric, the carbon fiber woven fabric and the carbon fiber knitted fabric. The experimental results show that:the peak values of both the reflectivity and transmittivity of the looping-grid structure compound fabric are relatively smaller than that of the other structure compound fabric. Therefore, the looping-grid structure compound fabric is the optimal absorption-type EM shielding material.