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   COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
                   School of Computational Sciences
                           (CSI 898-Sec 001)
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           Finite Element Modeling of Carbon Nanotubes

                          Michael Leamy
              The Mitre Corporation, McLean, VA

Carbon nanotubes, a nano-scale elemental form of carbon discovered in
1991 by Sumio Ijima, offer great promise as structural fibers,
electrical semiconductors, and hydrogen storage containers.  In each
case, large oriented assemblies of these tiny tubes will be necessary
before applications are a reality.  As such, this talk focuses on
modeling the dynamic behavior of the carbon nanotubes in the face of
external forcing.  An efficient explicit dynamic formulation appropriate
for modeling curved and twisted Carbon Nanotubes (CNT's) is presented
together with a finite element discretization incorporating atomistic
potentials.  This approach offers several advantages primarily related
to the model's computational efficiency: 1) the resulting partial
differential equations governing motion are in first-order form (i.e.
have first-order time derivatives only), 2) the system nonlinearities
appear at low order, 3) the intrinsic description incorporating
curvature allows low-order interpolation functions to describe generally
curved and twisted nanotube centerlines, 4) inter-element displacements,
slopes, and curvatures are matched at the element boundaries, and 5)
finite rotational variables are absent, along with their inherit
complexities.  In addition, the developed model and finite element
discretization are able to capture the nanotube's dynamic response,
without the expense of calculating the dynamic response of individual
atoms as per Molecular Dynamics models.  Simulation results are
presented which illustrate the dynamic response of a typical CNT to
axial, bending, and torsional loading.  Results from the simulations are
compared to similar results available in the literature, and close
agreement is documented.  
                        
                             September 12, 4:30 pm
               Room 206, Science & Tech. I, Fairfax Campus

Refreshments will be served at 4:15 PM.
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Find the schedule at http://www.scs.gmu.edu/lcdm/seminar/schedule.html
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