Modelling of mechanical failure due to constrained thermal expansion at the lightning arc attachment point in carbon fibre epoxy composite material

Examination of artificial lightning strike test damage suggests that mechanical loading contributes to some aspects of composite material degradation and failure. So far numerical work has focused on modelling resistive heating from the electrical load and a very limited number of studies have considered the thermal induced mechanical effects. Also preceding work which has modelled the effect of acoustic pressure loading has predicted the influence on specimen damage to be negligible. Thus the objective of this paper is to quantify the potential magnitude of the internal specimen mechanical loading resulting from electrical load induced thermal expansion. This is achieved through a simulation study and the definition of a bespoke modelling procedure to map specimen time dependent temperature from a thermal-electric analysis into a mechanical thermal-expansion analysis. The study compares predicted behaviour with measured test specimen damage. The results for the first time quantify the potential scale of loading resulting from constrained thermal expansion, the dimensions of induced damage and the strain rate magnitudes required for accurate material representation.