Analysis Of The Characteristics Of Surface Discharge On Frequency Selective Metamaterial Skin Under Impulse Voltage

Frequency selective metamaterials have excellent electromagnetic characteristics such as high in-band electromagnetic transmittance and strong off-band cutoff ability,and are very promising advanced aircraft stealth radome materials.There are a large number of metal arrays in this metamaterial,and the lightning shield failure rate is high,because the lightning attachment characteristics and process of the metamaterial are obviously different from that of the conventional radome.The layout design method of diverter strips for conventional radomes does not meet the requirements of lightning protection design for metamaterials.Surface discharge along the metamaterial skin has become a key physical factor affecting the layout of diverter strips.For this reason,the paper carrys out a study on the characteristics of surface discharge along the metamaterial skin under impulse voltage.The main contents are as follows.(1)A test platform for the surface discharge on skins of circular ring resonator frequency-selective metamaterials is designed.The influence of skin material,the grounding position,number of discharges and electrode structures on the length of the surface discharge(horizontal direction)on skins is studied.The results show that the grounding position has little influence on the length and morphology of surface discharge on metamaterial skins.The length of surface discharge on epoxy resin skin is the shortest,polyethylene skin in the middle,acrylic skin the longest.The length of the surface discharge on epoxy resin skins grows from 5 cm to 7cm with the increase in the number of discharges.The length of surface discharge under the spherical electrode is generally consistent with that under the needle electrode.(2)A charge scanning measuring device was designed to investigate the charge distribution and dissipation characteristics of skin surface after applying negative impulse voltage.The results show that charge distribution on the upper surface of the skin is negative and that on the lower surface is positive after surface discharge for epoxy resin skin / metamaterial and skin / aluminum plate structure.When the skin does not discharge along the surface under negative impulse voltage,the charge on the upper and lower surface of skin is negative,and the absolute value of charge density without surface discharge is much smaller than that with surface discharge.The surface charge distribution of the skin shows good symmetry without surface discharge.The surface charge distribution is related to the surface discharge morphology of the skin surface after surface discharge.The dissipation of the surface charge of the skin is affected by the three dissipation mechanisms: electric conduction along the surface of the skin,conduction through the volume of the skin,charge neutralization by gas ions.(3)The chain equivalent circuit model is used to analyze the factors affecting the length of surface discharge on the skin.The results show that the changes of the grounding horizontal distance does not cause the change of the impedance distribution of the discharge circuit,so it will not lead to the change of length of surface discharge on metamaterial skins.Different electrical parameters of three skins(dielectric constant,surface resistivity and surface charge deposition)result in different length of surface discharge on three skins.The increase of the number of skin discharges will lead to the increase of the deposition charge on the skin surface and reduce the surface resistivity of the skin,which will lead to the extension of the length of surface discharge.However,when the deposition of the surface charge and the decrease of the surface resistivity reach saturation,the length of surface discharge on the skin will no longer change.