Mechanisms of damage propagation in carbon composites under high impulse current magnitudes

In this investigation, the damage caused by large-magnitude lightning impulse currents was studied in the low Amperes and high kiloamperes current ranges. For the low current up to 350A tests, 150 mm × 150 mm square carbon composite material samples with a thickness of 2 mm and having a fastener and metal ring were used. For the high current tests using the D Waveform with magnitudes up to 70kA, two square samples of 550 mm × 550 mm were used with a thickness of 5 mm. The dent depth and ply level damage due to the waveform D lightning impulse current was estimated using scanning electron microscopy. It was found that the mechanical strength for samples impacted with 350 A current did not show any significant change in mechanical parameters whereas mechanical strength was considerably reduced for samples subjected to lightning current of more than 11kA magnitude.