Modeling of the Electric Arc Plasma Discharge Produced by a Lightning Strike Continuing Current

Despite the superior properties of the carbon fiber reinforced polymer matrix (CFRP) composites, such as the high strength-to-weight ratio, low coefficient of thermal expansion, excellent corrosion and fatigue resistances, the susceptibility of such composites to lightning strike damage still remains a concern to the aerospace industry. Although CFRP composite is considered electrically conductive, its electrical conductivity is still substantially lower than that of the metallic materials. For example, the electrical conductivity that of carbon fiber is around 1×10-3 times that of the copper. During a lightning strike discharge, the pulsed current can rise up to 30 ~ 200 kA with a duration of several microseconds and the continuing current can reach 200 ~ 800 A with a duration of 0.25 ~ 1 seconds. The low conductivity of the composite makes it difficult to dissipate the intense electrical energy, which can cause significant damage to the composite structure. This paper will be devoted to the study of the electric arc behaviors, including the electric and magnetic field evolutions, arc expansion, current density, and temperature distributions within the lightning arc using an electric arc plasma discharge model. Such a plasma model was developed through the coupling of Maxwell’s equations, the energy balance equation, and the laminar flow equation, and implemented with COMSOL Multiphysics. The model was employed to study the behaviors of the electric arcs produced by a lightning strike continuing current between a tungsten cathode and a solid anode material in argon and air mediums. The lightning-plasma-induced heat flux impinges on the anode material surface was also predicted. The model was validated through comparisons with experimental data and other numerical results reported in the existing literature. After the model was successfully validated, it was employed to study the effect of arc gaps on the lightning plasma behaviors. In addition, the effect of using different anode materials, i.e., copper, aluminum, and steel on the heat flux that flows from the plasma into the material surface was also investigated. Our next step is to use the current model to predict the current density and heat flux that flow into a CFRP composite anode material.