SIMULATION OF COMPOSITE DAMAGE DUE TO LIGHTNING STRIKE

The use of composite laminates for primary aircraft structures like fuselage implies to take into account the lightning strike hazard. Lightning strike is a threat to both metallic or composite structures, and requires careful considerations from a certification standpoint. The main difference between metallic and composite materials lies in the poor conductivity properties of the latter. However only few public research activities focus on the study of lightning direct effects on the integrity of carbon fibre reinforced polymers (CFRP) structures Recent studies at Onera led to the development of a magneto-hydrodynamic model in order to simulate the lightning channel. The output of this model (direct heating, electric current and impose pressure to the lightning arc) can be used as boundary conditions for a finite element (FE) simulations of lightning strike on composite material. The aim of this study is to propose first a comprehension model of the thermo-electric phenomena focusing on the resulting damaging pyrolysis due to the thermo-electric boundaries conditions imposed by the lightning channel. Pyrolysis is a major damaging mechanism affecting thermal and electric conductivities as well as mechanical properties. Pyrolysis is driven by (i) dielectric breakdown due to high electric fields and conductivity anisotropy and (ii) volume severe heating due to the Joule effect. To take into account the evolutions of the boundaries conditions (Joule heating) and the material state, the thermo electric analysis is performed by a partitioned coupling algorithm which links an electrostatic finite element analysis with a transient thermal finite element analysis. First comparison of these simulation results with experimental data will be presented.