Vaporization of Metallic Protections During Lightning Strikes: Experimental Study and Model

To protect aircraft CFRP (Carbon Fiber Reinforced Plastic) structure against lightning strikes, the aircraft manufacturers use metallic protections like ECF (Expanded Copper Foil). In this work, we investigate the effects of lightning strikes on metallic protections. This experimental study has been done with a D waveform, one of the waveforms defined in the aeronautic recommendations corresponding to the constraint applied to the fuselage and a large part of the wings. It is an impulse wave, the current rises from 0 to 100 kA in 20 μs. Different types of protection layers have been studied: solid copper foil (SCF, 72 g.m-2 and 179 g.m-2), solid aluminum foil (27 g.m-2 to 135 g.m-2), expanded copper foil (ECF, 73 g.m-2 and 195 g.m-2) and bronze mesh (80 g.m-2). The samples are made by gluing a metallic protection on a fiberglass square panel 40 cm wide. For each sample, the temporal evolution of the vaporization has been measured following the light emissions through the back side of the sample, with a high-speed camera (up to 210 kHz frame rate). The results are satisfactory compared to a theoretical vaporization model assuming that all Joule energy in the protection layer contributes to the vaporization, and neglecting thermal diffusion and radiation losses. In this model, the thermal and state dependencies of the electrical conductivity are taken into account.