The Influence Of Protection Mode On The Lightning Damage Of Carbon Fiber Composite

The carbon fiber reinforced polymer(CFRP)used on the outer surface of the aircraft usually has a lightning protection layer on the surface layer,such as flame sprayed aluminum and copper mesh.The electrical conductivity of the lightning protection layer is much higher than that of the carbon fiber material itself.When lightning strikes,the protection layer replaces the carbon fiber material to conduct lightning current,thereby protecting the carbon fiber material itself with low conductivity.Different protection methods have different protection characteristics,and the impact on the weight is not the same,the general metal mesh structure is lighter than the metal coating weight,the protection performance of the two also have some differences.In this paper,first,a non-standard low peak pulse current is injected into a test piece of the same layer of copper mesh protection and unprotected carbon fiber composite materials.The current distribution of protected and unprotected carbon fiber composite materials and metal aluminum plates under current injection is compared and analyzed through experiments and simulations.Lightning damage tests were carried out on the carbon fiber composites with no protection,flame sprayed aluminum and copper mesh protection by using the combined lightning current component of aircraft lightning 2A zone as stipulated in the standard,and analysis was carried out according to the damage morphology and non-destructive flaw detection results.Finally,through the COMSOL finite element simulation software,an electric-thermal coupling analysis model is established to study the current density and temperature field distribution of carbon fiber composite materials under different protection methods under the injection of combined lightning component in Zone 2A.The main conclusions are as follows:(1)When the lightning current is attached to the unprotected carbon fiber composite laminate,the current distribution on the surface is mainly related to the direction of the outermost carbon fiber laminate,and the current density is concentrated along the direction of the fiber laminate.The current distribution on the surface of the carbon fiber composites protected by copper mesh is more uniform than that of the carbon fiber composites without protection,and the current amplitude in the direction of thickness is much smaller than that of the carbon fiber composites without protection.(2)Under the lightning 2A zone,the unprotected carbon fiber composite laminates are seriously damaged,and the damage shape is related to the direction of the laminates.The use of metal copper mesh and flame sprayed aluminum can greatly reduce the carbon fiber composite material lightning damage.The shape of the damage of the flame sprayed aluminum protective layer is approximately circular,and the damage of the copper mesh is similar to the shape of the copper mesh itself.(3)In the simulation,the D component of the lightning current injected first in the lightning 2A zone is the main cause of the electrothermal damage of the carbon fiber,and the subsequent B and C * components cause less electrothermal damage.The damage of each layer of the unprotected carbon fiber composite material is mainly determined by the layup of the laminate.The damage shape of the carbon fiber composite material protected by flame sprayed aluminum and copper mesh is basically similar to the test results.The thicker the flame sprayed aluminum layer,the better the protection against lightning strikes.