Carbon fibers electrical measurements pave way for lightning strike
protection technologies

Date:
September 21, 2021
Source:
American Institute of Physics
Summary:
Carbon fiber reinforced polymer composite structures are important
in several industries, yet the electrical behavior of a composite
is challenging to measure or predict because of the electrical
conductivity of constituent carbon fibers and the composite's
complex hierarchical microstructure. Researchers report a direct
measurement of the transverse electrical resistivity of a single
carbon fiber. The researchers combined a precise sample preparation
with a technique called the van der Pauw method to accomplish this
challenging measurement.



FULL STORY ========================================================================== Carbon fiber reinforced polymer composite structures are serving an increasingly important role in aerospace, infrastructure, energy
generation, and transportation. Yet, the electrical behavior of a
composite is challenging to measure or predict because of the electrical conductivity of constituent carbon fibers and the composite's complex hierarchical microstructure.


==========================================================================
In Journal of Applied Physics, by AIP Publishing, researchers from
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 a precise sample preparation with a
technique called the van der Pauw method to accomplish this challenging measurement.

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

When carbon fibers are made, the strong carbon-carbon covalent bonds
are aligned in planes parallel to the fiber axis in the longitudinal
direction.

Only weak van der Waals bonds exist between the planes in the transverse direction, leading to directionally 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. The resistance measurements were performed on a slice 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 resistivity
of thin films or discs. The researchers cut and manipulated a slice of
carbon fiber using a focused ion beam and a needle, a tool more commonly
used to prepare transmission electron microscopy specimens.

The researchers are now 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 cross each other.

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

"This procedure may also be applied to other homogenous conductive fibrous materials with a diameter on the order of microns such as conductive
polymer fiber or metallic fiber," said Sottos.

========================================================================== Story Source: Materials provided by American_Institute_of_Physics. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Satoshi Matsuo, Nancy R. Sottos. Single carbon fiber transverse
electrical resistivity measurement via the van der Pauw
method. Journal of Applied Physics, 2021; 130 (11): 115105 DOI:
10.1063/5.0060126 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210921172709.htm

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