The overall goal of the present research is to provide a computationally based
methodology to realize the projected extraordinary properties of Carbon Nanotube (CNT)-
reinforced composites and polymeric nanofibers for engineering applications. The
discovery of carbon nanotubes (CNT) and its derivatives has led to considerable study
both experimentally and computationally as carbon based materials are ideally suited for
molecular level building blocks for nanoscale systems. Research in nanomechanics is
currently focused on the utilization of CNTs as reinforcements in polymer matrices as
CNTs have a very high modulus and are extremely light weight.
The nanometer dimension of a CNT and its interaction with a polymer chain
requires a study involving the coupling of the length scales. This length scale coupling
requires analysis in the molecular and higher order levels. The atomistic interactions of the
nanotube are studied using molecular dynamic simulations. The elastic properties of neat
nanotube as well as doped nanotube are estimated first. The stability of the nanotube
under various conditions is also dealt with in this dissertation.
The changes in the elastic stiffness of a nanotube when it is embedded in a
composite system are also considered. This type of a study is very unique as it gives
information on the effect of surrounding materials on the core nanotube. Various
configurations of nanotubes and nanocomposites are analyzed in this dissertation.
Polymeric nanofibers are an important component in tissue engineering; however,
these nanofibers are found to have a complex internal structure. A computational strategy is developed for the first time in this work, where a combined multiscale approach for the
estimation of the elastic properties of nanofibers was carried out. This was achieved by
using information from the molecular simulations, micromechanical analysis, and
subsequently the continuum chain model, which was developed for rope systems. The
continuum chain model is modified using properties of the constituent materials in the
mesoscale. The results are found to show excellent correlation with experimental
measurements.
Finally, the entire atomistic to mesoscale analysis was coupled into the macroscale
by mathematical homogenization techniques. Two-scale mathematical homogenization,
called asymptotic expansion homogenization (AEH), was used for the estimation of the
overall effective properties of the systems being analyzed. This work is unique for the
formulation of spectral/hp based higher-order finite element methods with AEH. Various
nanocomposite and nanofibrous structures are analyzed using this formulation.
In summary, in this dissertation the mechanical characteristics of nanotube based
composite systems and polymeric nanofibrous systems are analyzed by a seamless
integration of processes at different scales.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1469 |
| Date | 15 May 2009 |
| Creators | Unnikrishnan, Vinu Unnithan |
| Contributors | Reddy, J. N. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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