Coupled thermal electrical and mechanical lightning damage predictions to carbon/epoxy composites during arc channel shape expansion

This paper presents a new finite element (FE) methodology to predict highly nonlinear, transient thermal-electrical-mechanical responses of carbon/epoxy laminates subjected to simulated lightning currents. A series of fully coupled thermal-electrical-structural analyses was performed to characterize effects of radially and asymmetrically expanding lightning arc channels on coupled thermal, electrical, and mechanical damage in AS4/3506 carbon/epoxy laminates subjected to relatively low (40 kA) peak lightning currents. Surface current, electromagnetic pressure, and shockwave overpressure were applied on the spatially- and temporally-varying circular and elliptical arc channel areas impinged on the composite surface. The FE predictions were validated with the physical lightning damage observed in laboratory-generated strikes. The predicted electrical, thermal, and mechanical responses were strongly influenced by the arc channel shape, expansion, surface current magnitudes, and mechanical pressures applied inside the arc channels. The domains of the predicted current density, electrical potential, temperature increases, and thermal strain distributions were primarily elongated along the composite outermost layer's fiber direction due to the primary electrical conduction and Joule heating occurring along this direction. The total strain and stress distributions were influenced by both thermal expansion (due to an extremely rapid temperature change) and deformation (due to mechanical pressures). The FE models showed that the predicted thermal damage in an expanding elliptical arc channel most closely matched with observed physical lightning damage. This study suggests lightning responses of carbon/epoxy laminates strongly depend on various arc channel parameters. Using more realistic arc channel parameters should lead to better agreements with experimental results.

Automated summary

This paper presents a new finite element methodology to predict highly nonlinear, transient thermal-electrical-mechanical responses of carbon/epoxy laminates subjected to simulated lightning currents. The FE predictions were validated with the physical lightning damage observed in laboratory-generated strikes. The predicted responses were strongly influenced by arc channel parameters, suggesting that using more realistic parameters can lead to better agreements with experimental results.