Experimental And Simulation Study On Lightning Damage Of Carbon Fiber Composites

Carbon fiber reinforced polymer(CFRP)composites has been widely used in aerospace materials due to its excellent mechanical properties and low density.However,the conductivity of carbon fiber composite is quite different from that of metal,which will produce high temperature when it is struck by lightning and cause serious damage to the material.Therefore,it is of great significance to study the lightning damage mechanism of CFRP for aircraft lightning protection.At present,scholars at home and abroad have carried out a large number of experiments and simulations on the influence of arc and Joule heating on lightning damage of composite materials,but there is a lack of research on the influence of mechanical factors such as gas impact on material damage.Lightning stroke of carbon fiber composite is a process of multi-physical field coupling,and the stacking sequence of composite is complex.It is necessary to conduct decoupling analysis to study its lightning damage mechanism.Fasteners are usually used for mechanical connection of aircraft.The structure of carbon fiber composites with fasteners is complex,so the research on lightning damage of carbon fiber composites with fasteners becomes a difficult problem.In this paper,the lightning damage mechanism and prediction model of carbon fiber composites were studied as follows:(1)The test and observation platform of carbon fiber composite materials was built.A 20 k A impulse current generator system was designed and built to carry out lightning impulse and temperature rise test of cast material of carbon fiber and epoxy resin under low current.A 100 k A impulse current generator system was built to study the lightning damage and spark discharge of carbon fiber composite.(2)Casting samples with different carbon fiber mass fraction were prepared to study the influence of numbers of carbon fiber bundles on lightning damage.The lightning damage degree of the casting material is proportional to the number of carbon fiber bundles,indicating that Joule heating is an important factor in causing the lightning damage of casting material.(3)The lightning damage test and electro-thermal coupling simulation analysis of carbon fiber composite were carried out.The experimental results showed that the carbon fiber composites with fasteners had bright filamentous arc when struck by lightning,and the carbon fiber composites without fasteners had continuous combustion when struck by lightning.The simulation results showed that when the lightning current amplitude was 39 k A,the temperature of carbon fiber composite without fasteners could reach 3000 °C,the amplitude of surface electric field intensity could reach 20 k V/mm and the amplitude of potential could reach 5 k V.Under the same conditions,the temperature,electric field strength and potential of CFRP with fasteners were lower than those of CFRP without fasteners.(4)By establishing the simulation model of the damage generated by gas expansion onto CFRP,the research shows that gas expansion is the main factor of composite material lightning damage at high energy.An electric-thermal-mechanical coupling prediction model was established,which combined the influence of Joule heat and gas expansion.The model can accurately predict the lightning damage area of carbon fiber.When the Joule heat was 2.173 k J and 4.245 k J,the maximum error of the composite model was 12.5%.