Modeling and Characterization of Elastic Constants of Functionalized Nanotube Materials
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Modeling and Characterization of Elastic Constants of Functionalized Nanotube Materials S. J. V. Frankland1, M. N. Herzog2, G. M. Odegard1, T. S. Gates3, C. C. Fay3 1 National Institute of Aerospace, Hampton, VA 2 National Research Council, Hampton, VA 3 NASA Langley Research Center, Hampton, VA ABSTRACT Molecular dynamics simulation and equivalent continuum modeling were used to calculate the elastic constants of 1,3-bis(4-aminophenoxy-4'-benzoyl) benzene (1,3-BABB)/single-walled carbon nanotube (SWNT) materials. The calculated Young’s moduli are compared with storage moduli measured experimentally with nanoindentation. Excellent agreement is observed between the calculated and measured modulus values for the 1,3-BABB/SWNT materials. INTRODUCTION Nanostructured materials are defined as those having at least one constituent that has nanoscale dimensions. The structure of such materials can often be controlled during material synthesis in order to influence the bulk or engineering-level properties. However, without the proper insights into the details of the structure-property relationships, the development of nanostructured materials with tailored mechanical properties would be an expensive process of trial-and-error. Multi-scale modeling and predictive simulation is one approach to providing these insights and reducing the cost and time involved with material design and scale-up. Carbon nanotubes are a novel type of nanostructured material that have well-defined molecular structure and the potential for increasing the mechanical performance of nanotube based composite materials. It is recognized that if one can alter (functionalize) the molecularlevel interface between adjacent nanotubes or the nanotube-to-polymer interface in a composite, then the resultant mechanical properties of the bulk material could be enhanced. It is the potential for this chemical bond between nanotubes, herein described as a “tether,” to increase mechanical stiffness of nanotube composites, that provides the motivation for this current study. The objective of this work is, therefore, to use multi-scale methods to computationally predict the mechanical properties of a tethered nanotube material and to compare the model predictions with the experimental measurements. Molecular simulations and equivalent continuum modeling are the methods used to predict the elastic stiffness constants of this material. These computed results are compared with measured storage modulus values of the tethered material.
MATERIAL DESCRIPTION The tethered nanotube material consists of single-walled carbon nanotubes (SWNT) covalently linked by 1,3-bis(4-aminophenoxy-4'-benzoyl) benzene (1,3-BABB) (Figure 1). Three 1,3-BABB/SWNT materials were prepared by reacting SWNTs with 1,3-BABB in the presence of dichlorobenzene and isoamyl nitrite using the synthetic method developed by Tour
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Figure 1. Chemical structure of 1,3-BABB. and coworkers [1]. In this reaction the amine groups are removed from 1,3-BABB which, in turn, chemica
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