Numerical estimations of lightning-induced mechanical damage in carbon/epoxy composites using shock wave overpressure and equivalent air blast overpressure

A new approach is proposed for predicting lightning-induced mechanical damage using the shock wave overpressure (SWO) due to lightning arc channel expansion and also its equivalent air blast overpressure (ABO) due to an explosion of chemical potential energy in AS4/3506 carbon/epoxy laminates. The SWOs and equivalent ABOs associated with 124, 247, and 494 kA peak lightning currents were considered. Dynamic responses of the composite laminates due to both the SWOs and ABOs were similar to each other. The spatial variations in the peak compressive and tensile midplane displacements evaluated near the laminate center showed that mechanical damage tended to be symmetric about the laminate midplane. Hashin's four different damage criteria were implemented to predict fiber/matrix failures. The predicted failure index distributions in the carbon/epoxy plies were nearly identical for both SWOs and ABOs. Except for matrix tension failure predicted at the 494 kA peak current, all damage failure indices increased as the peak current increased, but were smaller than unity, implying no mechanical damage initiation due to lightning strike. These FE results suggest that lightning SWO may not cause significant mechanical damage and it may be possible to interchangeably use either SWO or ABO to predict lightning-induced mechanical damage.