Effects of electrophoretically deposited Carbon Nanofibers on the interface of single carbon fibers embedded in epoxy matrix
Schaefer, Joseph D.
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In this work, electrophoretic deposition (EPD) was used to deposit carboxylic acidfunctionalized carbon nanofibers (O-CNFs) and amine-functionalized carbon nanofibers (ACNFs) on the surface of single carbon fibers. Using the fiber fragmentation technique, the stress transfer at the single fiber interface was characterized by determining the interfacial shear strength (IFSS) for different fiber surface treatments. For the O-CNF investigation, samples for sized, unsized, O-CNF deposited sized, and O-CNF deposited unsized carbon fibers were tested. The A-CNF investigation was completed for sized carbon fibers acting as the anode during EPD for single and double concentrations of CNFs in water. Additionally, results for fibers acting as both the anode and cathode during a two-stage A-CNF deposition process are provided. Finally, the effects of EPD were investigated by testing fibers acting as the cathode or anode in water without the presence of O-CNFs or A-CNFs. Weibull analyses of single fiber tensile failures were performed to account for scale effects along the fiber length and support IFSS estimation. This research was aimed at obtaining a fundamental understanding of how functionalized CNF addition, EPD electric field setup, and fiber sizing affected IFSS and fiber surface morphology. Additionally, the processing effects on single fiber tensile strength were determined. It was shown that removing the sizing decreased the IFSS by 27%. One-stage addition of O-CNFs to the unsized interface increased the IFSS by 15% over the base sized fiber and 56% compared to the unsized fibers. One-stage cathodic deposition of O-CNFs on the single fiber surface led to the greatest IFSS increase of 215%. This IFSS increase is attributed to enhancement of surface roughness and surface area created by addition of the O-CNFs to the carbon fiber surface.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.