Lightning Protection
“Lightning protection systems are used to prevent or lessen damage to structures done by lightning strikes. Lightning protection systems mitigate the fire hazard which lightning strikes pose to structures. A lightning protection system provides a low-impedance path for the lightning current to lessen the heating effect of current flowing through flammable structural materials. If lightning travels through porous and water-saturated materials, these parts of a building may literally explode if their water content is flashed to steam by heat produced from lightning current.”
“Because of the high energy and current levels associated with lightning (currents can be in excess of 150,000 amps), and the very rapid rise time of a lightning strike, no lightning protection system can guarantee absolute safety from lightning. Lightning current will divide to follow every conductive path to ground, and even the divided current can cause damage. Secondary "side-flashes" can be enough to ignite a fire, blow apart brick, stone, or concrete, or injure occupants within a structure or building. However, the benefits of basic lightning protection systems have been evident for well over a century.”
Recent Journal Articles
Carbon Fiber–Bismaleimide Composites Filled with Nickel-Coated Single-Walled Carbon Nanotubes for Lightning-Strike Protection
(2527–2533)Advanced Functional Materials 21 #13 (2011)
Chakravarthi et al developed high-temperature bismaleimide (BMI)–carbon fiber composites filled with nickel-coated single-walled carbon nanotubes (Ni-SWNTs) based on three key factors: i) dispersion of Ni-SWNTs, ii) their surface coverage on the carbon plies and, iii) the composite surface resistivity. Atomic force microscopy analysis revealed that coating purified SWNTs with nickel enabled improved dispersion which resulted in uniform surface coverage on the carbon plies. The electrical resistivity of the baseline composite system was reduced by ten orders of magnitude by the addition of 4 wt% Ni-SWNTs (calculated with respect to the weight of a single carbon ply). Ni-SWNT–filled composites showed a reduced amount of damage to simulated lightning strike compared to their unfilled counterparts, as indicated by the minimal carbon fiber pull-out. (RDC 7/5/2011)