“Scale and Time Dependent Mechanics of Polymeric Nanofibers”

BROWN UNIVERSITY
Joint Materials/Solid Mechanics Seminar Series

“Scale and Time Dependent Mechanics of Polymeric Nanofibers”

Prof. Ioannis Chasiotis
Department of Aerospace Engineering
University of Illinois at Urbana-Champaign

Abstract:

The mechanical response of polymeric nanostructures as a function of size and strain rate is largely unexplored. This seminar will elaborate on the mechanical behavior of electrospun polymeric nanofibers at strain rates 10-4 - 200 s-1 as a function of their diameter and fabrication conditions. The experiments were conducted via MEMS tools in conjunction with digital image correlation motion tracking, which allowed for high resolution measurements in force and nanofiber extension. The advantage of this method lies with the ability to carry out nanoscale experiments in ambient conditions, contrary to commonly followed practices that require imaging with electron microscopy. The elastic modulus and the tensile strength of nanofibers with diameters between 200-800 nm varied by a factor of seven with fibers in the range of 200-300 nm resulting in the highest property values. Thinner fibers that demonstrated the highest mechanical strengths were characterized by molecular alignment which was confirmed by Fourier transform infrared spectroscopy. Most mechanical properties varied monotonically in the aforementioned range of strain rates, while they were a strong function of the nanofiber diameters and the necking instabilities occurring during the tensile experiments. These results supported the optimization of the fabrication method of electrospinning in order to produce amorphous polymeric nanofibers with true ultimate tensile strength as high as 900 MPa and ductility exceeding 200% at most applied strain rates.

Monday, April 19, 2010 - 4:00-5:00 pm - B&H Room 190