Fatigue of carbon nanotube-loaded polyacrylonitrile fibers
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The effects of loading polyacrylonitrile (PAN) single fibers with carbon nanotubes (CNTs) on mechanical damage accumulation processes are explored in this thesis. Tensile, fatigue, and creep experiments were conducted to establish the effects of CNTs on the strength, fatigue lifetime, and viscoelastic/plastic (creep) damage accumulation. Three different configurations were tested: neat PAN fibers, PAN fibers loaded with multi-walled CNTs (MWCNTs) in the core, and PAN fibers loaded with few-walled CNTs (FWCNTs) uniformly throughout. The tensile results yielded load and displacement data from which failure stress was determined for all three fiber groups. During stress-life fatigue tests (runout lives ~600,000 cycles) the fibers displayed similar fatigue susceptibilities, but in static load creep tests, the different fiber configurations led to a wider range of responses. The different fiber processing parameters used for each fiber group lead to a variety of viscoelastic and viscoplastic properties within each system, resulting in a range of damage accumulation mechanisms.