Development of carbon nanotube/epoxy nanocomposites for lightning strike protection

Sonication has been used to breakdown long aspect ratio tubes to short tubes, and a technique to quickly monitor this size reduction described. Nanocomposite samples consisting of these high and low aspect ratio carbon nanotubes have been produced at various weight fractions up to 1%. Test specimens for electrical, thermal and mechanical testing have been prepared and tests conducted. Differential scanning calorimetry has been used to monitor the cure cycle, confirm the extent of curing and measure the glass transition temperature of these nanocomposites materials. Thermal conductivity results have shown a 78% increase between the unloaded and 1% loaded specimens with high aspect ratio nanotubes. Results from the low aspect ratio tubes show a modest improvement of 7% increase in thermal conductivity at between the unloaded and 0.5% loading. Results from the mechanical testing have shown an overall decrease in the flexural modulus of the composites with increasing nanotubes weight fraction. The flexural strength of the materials, however, has been shown to increase with both high and low aspect ratio nanotubes. Electrical conductivity tests have shown a substantial increase in the conductivity at relatively low loadings of carbon nanotubes. The aspect ratios of the tubes have been shown to influence the percolation threshold and the overall current carrying capacity of the composite. Carbon nanotubes have previously been shown to improve physical and mechanical properties. The effect of aspect ratio on their enhancement and reinforcement potential has still to be fully investigated. It is fair to conclude, however, that due to their ability to improve a broad range of physical and mechanical properties at relatively low loadings, carbon nanotubes are a promising candidate to improve the lightning strike behavior of CFRP. Continuing work aims to study the effects on carbon nanotube aspect ratio on the rheological behavior to further understand the impact that this has on the processability of the carbon nanotube-epoxy dispersions.