Carbon fiber electrical measures pave the way for lightning protection

The carbon fiber wafer in the microelectric circuit is electrically connected to the gold / chromium electrodes with platinum / carbon electrodes.

Satoshi Matsuo and Nancy R. Sottos

WASHINGTON, DC – Carbon fiber reinforced polymer composite structures are playing an increasingly important role in aerospace, infrastructure, power generation and transportation. However, the electrical behavior of a composite is difficult to measure or predict due to the electrical conductivity of the constituent carbon fibers and the complex hierarchical microstructure of the composite.

In Journal of Applied Physics, by AIP Publishing, researchers at the University of Illinois at Urbana-Champaign report the first direct measurement of the transverse electrical resistivity of a single carbon fiber. The researchers combined precise sample preparation with a technique called the van der Pauw method to accomplish this difficult measurement.

“Our experiments confirm that the electrical properties measured across a carbon fiber are not the same as the properties measured along the length of the fiber,” said co-author Nancy Sottos.

When carbon fibers are made, the strong carbon-to-carbon covalent bonds are aligned in planes parallel to the axis of the fiber in the longitudinal direction. Only weak van der Waals bonds exist between planes in the transverse direction, leading to direction dependent properties.

The researchers used a technique known as the van der Pauw method to accurately measure the resistivity in the transverse direction of a carbon fiber. Resistance measurements were made on a wafer of carbon fiber cut using a focused ion beam and connected to electrodes for electrical resistance measurements.

“Our results reveal that an IM7 carbon fiber is more electrically conductive in the direction parallel to the length,” said co-author Satoshi Matsuo.

Previously, the van der Pauw method was mainly used to measure the resistivity of thin films or discs. Researchers cut and manipulated a slice of carbon fiber using a focused ion beam and a needle, a tool most commonly used to prepare transmission electron microscopy samples.

Researchers are currently working on electrical contact resistance measurements between two carbon fibers. The electrical contact resistance depends on the electrical resistivity and the contact area, which also varies depending on the angle at which the two fibers intersect.

Next, they plan to examine transverse electrical resistivity measurements on different types of carbon fibers with varying measurement conditions such as environmental temperature.

“This procedure can also be applied to other homogeneous conductive fibrous materials with a diameter of the order of a micron such as conductive polymer fiber or metallic fiber,” Sottos said.

– This press release was provided by the American Institute of Physics

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