Wednesday, 13 October 2004 - 2:40 PM

This presentation is part of : Failure of Ceramics and Ceramic Composites

Multiscale Modeling of Nanocrystalline Zirconia Nanofibers

S. Xue1, J. Bai2, C. Wang1, R. Feng1, and X. C. Zeng2. (1) Department of Engineering Mechanics, University of Nebraska-Lincoln, Lincoln, NE 68588, (2) Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE 68588

Continuous nanocrystalline ceramic nanofibers fabricated through sol-gel electrospinning process are expected to be super-strong yet ultra-flexible (with infinite length-to-width ratio). However, characterization of the mechanical properties of such a nanofiber remains a challenge. In addition to the statistical means and deviations of mechanical properties (such as Young's modulus) of the fiber, the critical fiber length, beyond which the statistical mean values can be meaningfully used as the representative material parameters needs to be determined. In order to address this issue, we have developed a multiscale modeling methodology, in which first-principles quantum mechanical calculations are used to determine the crystal elasticity and polycrystal simulations coupled with finite element (FE) analysis are utilized for statistical characterization of the elastic properties of the fiber. The technique has been applied to analyze the elasticity of nanocrystalline zirconia nanofibers. The elastic constants of three distinct polymorphous phases of zirconia are determined from the quantum mechanical calculations. The polycrystalline structures of the fibers are simulated using the three-dimensional Voronoi tessellation. Each polycrystal model is further divided, in a grain-wise but intergranularly consistent manner, into a tetrahedral element mesh for FE analysis. The numerical solution is further analyzed statistically to determine the distributions of stress, strain and elastic properties. The results are presented for the nanofibers of various diameters and with either pure monoclinic phase or a composition of 59% tetragonal phase and 41% monoclinic phase by volume. The statistical nature of the fiber elasticity and its dependences on crystal number density and fiber diameter are discussed.

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