Design And Experimental Research For Strong Electromagnetic Environment Protection Of Aircraft Composite Fuel Tank

With the increasing application of composite materials in modern civil aircraft fuel system,due to their poor electrical conductivity and low shielding effectiveness,the strong electromagnetic environment has become an important factor affecting the safe flight of aircraft.The strong electromagnetic environment faced by civil aircraft mainly includes Lightning and High-Intensity Radiated Fields(HIRF).In this paper,take the aircraft composite fuel tank as the research object,the combination of simulation and experiment is used to study the damage mechanism and protection characteristics of the aircraft composite fuel tank in the strong electromagnetic environment,and verify the effectiveness of aircraft composite fuel tanks in protection against the strong electromagnetic environment.The main research contents come as follows:1.Use COMSOL Multiphysics coupling simulation software to establish the unprotected and flame sprayed aluminum protective Carbon Fiber Reinforced Polymer Composites(CFRP)laminate model of the fuel tank box section skin,and study the temperature distribution and electro-thermal damage characteristics of each layer at different times under the injection of typical lightning current combination waveforms.And the influence of heat transfer on the electro-thermal damage characteristics of the model after the lightning current combined waveform injection is completed.Finally,the damage mechanism and causes of the above rules are analyzed.2.Through the lightning protection design of the aircraft composite fuel tank,then the direct effect damage test was carried out.The damage of the test piece protected by flame spraying under direct lightning current injection was obtained.Compared with the simulation results,it is found that the damage is relatively consistent,which verifies the correctness of the test and simulation and the effectiveness of protection.3.With the help of electromagnetic simulation software CST,a simplified model of aircraft fuel tank cabin was established.Firstly,the shielding effectiveness(SE)at different positions was studied,and then the influence of incident wave radiation direction,polarization mode and different protection methods on the shielding effectiveness of the fuel tank cabin was studied.Finally,the coupling mechanism and causes of the above laws are analyzed.4.Through the HIRF protection design of the composite fuel tank,the low-level sweep frequency field test and the fuel vapor ignition test in the reverberation chamber are carried out to obtain the shielding effectiveness of the composite fuel tank cabin in the HIRF environment and verify its stability.Through the test,it can be known that the shielding effectiveness of the internal position of the aircraft composite fuel tank after the protection design is related to the position of the hole,at the same time it has a similar amplitude and change law to the simulation result as a whole,thus verifying the correctness of the simulation and the effectiveness of the protection;Simultaneously,when the metal or composite material fuel tank is exposed to strong electromagnetic radiation,the arc or spark generated between the metal conductors is not easy to ignite the modern typical aviation fuel vapor in it,which proves that it has good stability in the HIRF environment.In summary,in this paper,systematic research on the damage mechanism and protection design of aircraft composite fuel tanks in the electromagnetic environment is carried out.The results can provide references for the strong electromagnetic protection of domestic aircraft composite fuel tanks.This has practical engineering significance for improving the airworthiness verification technology of domestic civil aircraft in the strong electromagnetic environment.