October 19, 2020
In a fraction of a second, a lightning bolt can strike with about 10,000,000,000 watts of electricity. It is an incredible amount of power that has awed and fascinated scientists for centuries. (Movie fans may be interested to know that 1.21 gigawatts is well within the range of some lightning bolts. The ability to harness it and use it to power a Delorean based time machine is still science fiction however.)
Both the power produced by lightning strikes and the damage they can cause are significant. On average, planes are hit by lightning once a year and damage from lightning strikes accounts for more than 23% of insurance claims filed by wind farms in the United States. Repairing damaged aircraft and turbine blades can be costly and often requires them to be taken out of service for a long period of time.
Both the aerospace and wind energy industries rely on carbon/glass fiber reinforced polymer matrix (CFRP) composite materials for structural materials. These composite materials can have high strength to weight ratios and excellent corrosion and fatigue resistance but their low electrical conductivity creates a difficult environment for electricity to be dissipated safely.
When a lightning bolt strikes composite material, the temperature in the material rises rapidly. That can eventually lead to resin vaporization, delamination, matrix cracking, fiber breakage and a substantial loss of strength, stiffness and structural service life.
“These components do not work well with electricity,” said mechanical and aerospace engineering Professor Yeqing Wang. “Lightning can produce electrical, thermal, magnetic, and mechanical effects on an aircraft.”
Wang was recently selected as a recipient of a competitive 2020-2021 Ralph E. Powe Junior Faculty Enhancement Award from the Oak Ridge Associated Universities. The award will help fund Wang’s research into making the next generation of composite materials more lightning resistant.
Aerospace companies currently use metal mesh wrapped around the carbon fiber composite to conduct electricity away. That mesh is heavy and adds to fuel consumption. A lightweight coating or a new composite that replaces heavy metal mesh could significantly reduce fuel costs and the cost of repairing bonding between mesh and aircraft.
“With the understanding we gain through our study, we hope to be able to tell manufacturers how to better protect wind turbines and aircraft,” said Wang. “We will be doing computational work and testing to determine failures in composite materials.”
To simulate the effects of a lightning strike on test materials, Wang will be working with the Mississippi State High Voltage Lab and Oak Ridge National Lab.
“We want to observe damage and understand what energy is consumed by fiber breakage or other damage modes,” said Wang. “It is a lot of physics and mechanics inside. We are trying to solve this puzzle.”