Electrophoretic Depositions of Carbon Nanotubes on Long Discontinuous Carbon Fibers

• Gianluca Tiso, Mechanical Engineering, University of Delaware

• Erik Thostenson, Mechanical Engineering, University of Delaware

Carbon fiber filaments exhibit positive piezoresistivity when subjected to uniaxial tensile strain, a property advantageous for various sensing applications. Meanwhile, carbon nanotubes (CNTs) are renowned for their exceptional mechanical, electrical, and thermal properties. Integrating a CNT film with carbon fiber composites promises to enhance their piezoresistive properties significantly. Preliminary single fiber testing has demonstrated that the gauge factor for uncoated fibers is ~1.7, whereas CNT coated fibers exhibit a gauge factor exceeding 25.

Electrophoretic deposition is an efficient method 

A critical challenge in this integration is maintaining fiber alignment and effective contact with the cathode during the coating process. This is because when fibers are submerged during the coating process fibers often wash away.

To address these challenges, two primary methods were explored. The first approach involved placing the carbon fibers under its carrier fabric. Here, discontinuous carbon fibers were covered with a nonwoven fabric, ensuring that the contact between the carbon fibers and the electrode was maintained during electrophoretic deposition (EPD).

The second method employed a commercial nylon mesh to cover the fiber mat. This mesh was directly taped to the electrode, which effectively limited fiber movement and prevented the fibers from washing away. This setup facilitated uniform CNT coating on the carbon fibers while also maintaining alignment.

Both methods resulted in a uniform CNT coating on the carbon fibers. The nylon mesh method was particularly effective in maintaining fiber alignment. Preliminary observations suggest that the thickness of the CNT film influences the mechanical properties of the carbon fiber composite.

This study presents a promising pathway for enhancing the piezoresistive properties of carbon fiber composites through CNT integration, highlighting the importance of innovative coating techniques and support materials. Further investigation is needed to optimize these methods and fully understand the impact of CNT film thickness on the composite’s mechanical properties.