Investigation of transverse electrical resistivity and electrical contact resistance of carbon fibers/carbon fiber composites

Matsuo, Satoshi

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https://hdl.handle.net/2142/116062 Copy

Description

Title

Investigation of transverse electrical resistivity and electrical contact resistance of carbon fibers/carbon fiber composites

Author(s)

Matsuo, Satoshi

Issue Date

2022-07-12

Director of Research (if dissertation) or Advisor (if thesis)

Sottos, Nancy R

Doctoral Committee Chair(s)

Sottos, Nancy R

Committee Member(s)

• Braun, Paul V
• Cahill, David G
• Chasiotis, Ioannis

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Carbon fiber
• Carbon fiber composite
• electrical resistivity
• electrical resistance
• van der Pauw Method
• four-point probe method

Abstract

The electrical properties of carbon fiber composites play an essential role in applications where multifunctionality is desired. When combined with an electrically insulating matrix material, carbon fibers are the only electrically conductive constituent; therefore, knowledge of the electrical properties of single carbon fiber is essential to understanding the bulk electrical properties of carbon fiber composites. In order to predict the bulk electrical conductivity of unidirectional carbon fiber composites, researchers have used the resistor network model, which requires the longitudinal electrical resistivity of single carbon fiber and the electrical contact resistance between two carbon fibers. However, studies of the electrical contact resistance between two carbon fibers are scarce. The transverse electrical resistivity required to calculate the electrical contact resistance between two carbon fibers also has not been reported. In this study, the transverse electrical resistivity of a single fiber, the electrical contact resistance between two fibers, and the interfacial electrical contact resistivity of unidirectional composite laminates are investigated. IM7 and AS4 fibers, carbon fibers used for aerospace composites, are chosen for this study. The transverse electrical resistivity measurements are performed by the van der Pauw method on single carbon fiber samples fabricated with focused ion beam and conventional photolithography techniques. The measured transverse electrical resistivity values of the IM7 and AS4 fibers are (9.3 ± 0.3) × 10-5 Ωm and (6.3 ± 0.3) × 10-5 Ωm, respectively. The IM7 fibers have approximately six times higher transverse electrical resistivity than the longitudinal value. In comparison, the transverse electrical resistivity of the AS4 fibers is roughly four times greater than the longitudinal value. The electrical contact resistance between two carbon fibers is calculated as a function of angles between fibers and the applied force using the measured transverse electrical resistivity values, Hertz contact theory, and Holm’s theory. The electrical contact resistance between two carbon fibers monotonically increases as the angle between the fibers approaches 90º. A four-point probe protocol is developed to measure the electrical contact resistance between two carbon fibers. The theoretical and experimental values agree reasonably well. Interestingly, the AS4 fibers have a slightly non-linear V-I response and a significant electrical asymmetry at a small fiber angle, which is attributed to multiple contacts between the two fibers due to the non-smooth surface of the fibers. The interfacial electrical contact resistivity of unidirectional carbon fiber composite laminates is also characterized by a four-point probe method for varying curing pressures, layup angles, and current conduction modes. Overall, the interfacial electrical contact resistivity decreases as layup angles vary from 0º to 90º. The trend is affected by fiber types and curing pressures. The current conduction modes primarily affect the magnitude of the interfacial electrical contact resistivity. Also, the effects of surface sanding above the apparent contact area with sandpaper on the interfacial electrical contact resistivity are investigated.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Satoshi Matsuo

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