In-strike dynamical measurements of contact resistances

Assemblies representative of aircraft junctions made of two materials and a fastener have been subjected to lightning current waveforms in laboratory. Current distributions on the different parts of the assemblies have been measured. An electrical equivalent circuit of the assemblies has been built. An inverse method has been designed to extract the dynamical in-strike electrical parameters (resistances, inductances, generators) of the circuit from the measured current distributions. It is shown in particular that the in-strike contact resistances between the different parts are systematically very small, even when the pre- or post-strike values are large. This effect is related to the appearance of internal discharges in the gaps of the assembly.