Epoxy resin with carbon nanotube additives for lightning strike damage mitigation of carbon fiber composite laminates

Carbon fiber composites are paving the way for light weight, high strength structures in the aerospace industry. While the benefits of carbon fiber composites are undeniable, they also have their drawbacks. Crippling damage due to lightning strikes is one of them. The current solutions to reducing the damage due to lightning includes adding expensive and heavy copper mesh into the laminate. A potential solution to this problem would be to add a lightweight conductive additive to the epoxy resin instead of a copper mesh. Carbon nanotubes are chosen as the additive to create an electrically conductive resin matrix and hence increase the overall electrical conductivity of the composite. Increasing the conductivity will decrease the damage owing to a faster dissipation of lightning-strike-induced Joule heating, and more importantly increase the residual strength. In this work, we quantified the increase in conductivity through measuring the electrical resistance using the four-probe method. Results showed that the electrical resistance of the sample with carbon nanotube additives is 31% lower than the one with no additives when the same resin system is used. In addition, lightning strike tests have also been carried out with both samples using an artificially generated waveform A impulse current with a peak of 100 kA. The current results showed no visible damage to both the samples with and without CNT additives in the epoxy. Time-resolved camera images taken for the lightning strike tests showed that the lightning current may have conducted through the metallic grounding device owing to the small planar sample size (i.e., 6 by 6 inches), which resulted in unsatisfactory test results.