11/12/2009
MASE Colloquium: "Size & Time Dependent Mechanics of Polymeric Nanofibers"
2:30 PM
Lopata Hall, Room 101
Presented by Ioannis Chasiotis
Aerospace Engineering
University of Illinois at Urbana Champaign, Urbana, IL
Abstract:
Polymeric nanofibers are versatile building blocks for lightweight and multifunctional materials and structures. Their mechanical response as a function of size and strain rate is largely unexplored. In this work, the mechanical deformation of electrospun polyacrylonitrile (PAN) nanofibers at strain rates 10-4 - 200 s-1 was investigated as a function of their fabrication parameters by using a novel MEMS-based experimental method allowing for high resolution measurements in ambient conditions. Process optimization resulted in PAN nanofibers with true ultimate tensile strength as high as 900 MPa and ductility exceeding 200%. The elastic modulus and the tensile strength of PAN nanofibers with diameters between 200-800 nm varied by a factor of seven with nanofibers in the range of 200-300 nm having the highest property values. The thinner fibers that demonstrated the highest mechanical strength were characterized by molecular alignment which was shown by Fourier Transform Infrared (FTIR) measurements. Moreover, most mechanical properties of the PAN nanofibers varied monotonically in the above range of strain rates, while they were still a strong function of the nanofiber diameter. Finally, creep experiments provided the size dependent viscoelastic constants for the PAN nanofibers, which were shown to predict the nanofiber mechanical response at slow strain rates as a function of their diameter.
Mechanical, Aerospace & Structural Engineering
Linda Buckingham, (314) 935-8072
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