Study of damage characteristics in composite structures from simulated lightning strikes

This work investigated experimentally the direct effects of simulated lightning strikes in carbon/epoxy and E-glass/epoxy laminates. The direct effects were represented by Joule heating and kinetic shock waves. The experimental set-up was designed to maximize these direct effects by employing a solid electrode, pointed vertically to the surface of the specimens with a small electrode gap. The damage mechanisms were found to be in the form of resin sublimation, delamination and fibre tufting. The damage characteristics depended on type of composite materials, lightning current and action integral. In the carbon/epoxy laminates, resin sublimation and degradation were dominant at relatively low currents and with the further increase in current fibre tufting appeared due to kinetic shock waves. Penetration into the laminates was found to be limited to the only top two plies in the extreme case. The damage characteristics of the E-glass/epoxy laminates with a tiny hole were dominated by extensive delamination due entirely to shock waves with little sign of Joule heating. Analytical work will be desired to aid establishment of relationships between the damage characteristics and the lightning strike parameters via lightning channel radius and raised temperatures.