Electromagnetic Protection Testing And Evaluation Technology For Carbon Fiber Composites

With the development of science and technology,carbon fiber composite materials have been widely used in module housings,chassis cabinets,and other devices.Especially because of the characteristics of light weight,high strength,and stiffness,carbon fiber composite has been favorable to be used in aircraft fuselage material.Meanwhile,the electromagnetic protection performance of carbon fiber composite materials in the field of radio frequency(RF),magnetic field,and lightning pulse field will directly affect the electromagnetic compatibility of the aircraft,which will cause a great impact on the aircraft flight safety.In this paper,the transfer resistance of the carbon fiber composites under RF field,the equivalent conductivity under the magnetic field and the pulse impedance under the lightning pulse field are studied.In view of the three aspects above,first of all,in order to study the test method for the ability of carbon fiber composite material to transfer a surface current to another surface voltage in an RF field environment,the concept of RF transfer impedance is introduced in this paper.A RF transmission coaxial test device with a frequency limit of 1 GHz was designed and manufactured.The key parameters of the device were simulated and optimized using HFSS.Then the performance of the device is tested.The test results show that the test range is 0~1GHz,and the VSWR is lower than 1.25 in this range.The trend and size are basically consistent with the simulation results.Finally,the device was used to test carbon fiber composite materials.From four independent test results,it can be seen that the test repeatability is good,and the maximum deviation of the repeated test is 3dB.Then,in order to study the test method for the conductive properties of carbon fiber composite in a magnetic field environment,the concept of equivalent conductivity was introduced.First of all,theoretically,the relative conductivity was deduced based on the magnetic shielding effectiveness of the flat plate material.Then the magnetic shielding effectiveness of the carbon fiber composite material below 1 MHz was tested by the small loop antenna method,and the equivalent conductivity was deduced from the measured results.Finally,the results are verified by HFSS simulation.The simulation results are basically consistent with the measured results.Finally,in order to study the test method of impedance characteristics of carbon fiber composite under the lightning pulse field,the concept of pulse impedance was introduced.The commonly used waveforms of lightning direct effects are introduced and the appropriate waveforms are selected.Then based on a variety of experimental methods,a method for testing pulse impedance of carbon fiber composites was proposed.Finally,the parameters selected in the test,including current amplitude,electrode size and electrode material,are defined to lay the foundation for future research and testing.