Lightning Protection of Composite Aircraft Structures

Abstract:
Mechanical loads induced by lightning strikes in protected carbon fibre-reinforced polymer (CFRP) structures arise mainly from the overpressure due to the near-surface explosion of the lightning protection layer, from the shock waves caused by the supersonic expansion of the hot plasma channel, and from the magnetic forces induced by the current flow in the electrically conducting structures. Although the surface explosion of a protected CFRP leads to the highest pres-sures, the contributions of the supersonic expansion of the hot plasma channel and of the magnetic pressures cannot be neglected. This work presents an implementation of physically-based models of lightning-induced mechanical loads into a finite element framework combined with a modified continuum damage mechanics model for CFRPs. This novel ap-proach predicts the response of composite structures subjected to lightning strikes without the need to fit the model pa-rameters or recourse to experimentally determined parameters. The predictions agree well with experimental results and provide a new insight on the physics of the lightning-induced damage of composite structures.