Date of this Version
C. Ren, PAN Nanofibers and Nanofiber Reinforced Composites, M.S. Thesis, University of Nebraska-Lincoln, 2013
Nanomaterials play an important role in the development of nanotechnology. They possess unique mechanical, physical, and chemical properties coupled with small size and ultrahigh surface area that can provide critical advantages for applications. Continuous nanofibers attract special interest due to their dual nano-macro nature and ability to bridge scales. Nanofibers are being considered for a broad range of applications spanning advanced filters, separation membranes, ultrasensitive sensors, micro/nano actuators, nanoprobes, tissue engineering scaffolds, protective and smart closing, and multifunctional composites. Most of these applications require certain mechanical properties and robustness. However, the literature on the mechanical behavior of nanofibers and their assemblies and composites is very sparse. The objective of this thesis was to manufacture and study the mechanical behavior of nanofiber networks and nanofiber reinforced composites with several nanofiber orientation distributions. Uniform diameter ployacrylonitrile (PAN) nanofibers were manufactured using electrospinning technique. In order to find the optimum manufacturing conditions, the effects of several electrospinning process parameters on PAN nanofiber diameters and orientation distributions were analyzed systematically experimentally. Nanofiber morphologies were examined and statistically quantified by scanning electron microscopy. Non-linear mechanical properties of single nanofibers and aligned and random nanofiber networks were investigated and compared. Aligned and random PAN nanofiber reinforced composites were fabricated and their anisotropic fracture properties were evaluated experimentally for the first time. It was shown that a small amount of nanofiber reinforcement produced significant improvements in fracture toughness of epoxy-based nanocomposites. The results of this study can be used in the development of nanofibrous materials and applications requiring a degree of mechanical robustness.
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