Lightning mechanical damage prediction in carbon/epoxy laminates using equivalent air blast overpressure

Abstract

We propose a new, alternative approach to predict lightning mechanical damage in AS4/3506 carbon/epoxy laminates using equivalent air blast overpressure (ABO). Three lightning mechanical damage models are presented: i) the Shock Wave Overpressure (SWO) model, ii) the Conventional Weapons Effects Program (CONWEP) ABO model, and iii) the Coupled Eulerian-Lagrangian (CEL) ABO model. SWOs were determined from classical shock wave theory and the arc channel energy balance equation, and directly applied within pre-described arc channel areas. ABOs in the CONWEP and CEL models were calculated for equivalent TNT explosions and applied over the entire laminate surface. In contrast to the SWO and CONWEP models, the CEL model simulated the coupled fluid-structure interactions of the blast waves with the composite structures. Although the fundamental physics was different, both SWO and ABO induced similar dynamic structural responses and damage behavior within AS4/3506 carbon/epoxy laminates. The fiber and matrix failure, predicted using Hashin's four failure criteria, was not imminent at any of these peak currents. This implies that purely mechanical in-plane damage is unlikely to occur and thus is not a major concern for lightning strikes. This study shows that the ABO models can be used to predict lightning mechanical damage in composite structures as an alternative to a complex SWO model.