dc.contributor.author | Seifert, David Ryan | en_US |
dc.date.accessioned | 2018-11-30T09:00:44Z | |
dc.date.available | 2018-11-30T09:00:44Z | |
dc.date.issued | 2018-11-29 | |
dc.identifier.other | vt_gsexam:17725 | en_US |
dc.identifier.uri | http://hdl.handle.net/10919/86195 | |
dc.description.abstract | This thesis presents the design of multifunctional structures through the optimal placement
of nanomaterial additives. Varying the concentration of Carbon Nanotubes (CNTs) in a
polymer matrix affects its local effective properties, including mechanical stiffness, electrical
conductivity, and piezoresistivity. These local properties in turn drive global multifunctional
performance objectives. A topology optimization algorithm determines the optimal distribution
of CNTs within an epoxy matrix in an effort to design a set of structures that are
capable of performing some combination of mechanical, electrical, or peizoresistive functions.
A Pareto-Based Restart Method is introduced and may be used within a multi-start gradient
based optimization to obtain well defined multiobjective Pareto Fronts. A linear design
variable filter is used to limit the influence of checkerboarding. The algorithm is presented
and applied to the design of beam cross-sections and 2D plane stress structures. It is shown
that tailoring the location of even a small amount of CNT (as low as 2 percent and as high as
10 percent, by volume) can have significant impact on stiffness, electrical conductivity, and
strain-sensing performance. Stiffness is maximized by placing high concentrations of CNT
in locations that either maximize the bending rigidity or minimize stress concentrations.
Electrical conductivity is maximized by the formation of highly conductive paths between
electrodes. Strain-sensing is maximized via location of percolation volume fractions of CNTs
in high strain areas, manipulation of the strain field to increase the strain magnitude in these
areas, and by avoiding negative contributions of piezoresistivity from areas with differing net
signed strains. It is shown that the location of the electrodes can affect sensing performance.
A surrogate model for simultaneous optimization of electrode and topology is introduced
and used to optimize a 2D plane stress structure. This results in a significant increase in
sensing performance when compared to the fixed-electrode topology optimization. | en_US |
dc.format.medium | ETD | en_US |
dc.publisher | Virginia Tech | en_US |
dc.rights | This item is protected by copyright and/or related rights. Some uses of this item may be deemed fair and permitted by law even without permission from the rights holder(s), or the rights holder(s) may have licensed the work for use under certain conditions. For other uses you need to obtain permission from the rights holder(s). | en_US |
dc.subject | Topology Optimization | en_US |
dc.subject | Carbon Nanotubes | en_US |
dc.subject | Multifunctional Materials | en_US |
dc.subject | Micromechanics | en_US |
dc.subject | Analytic Sensitivities | en_US |
dc.subject | Strain Sensing | en_US |
dc.title | Topology Optimization of Multifunctional Nanocomposite Structures | en_US |
dc.type | Dissertation | en_US |
dc.contributor.department | Aerospace and Ocean Engineering | en_US |
dc.description.degree | Ph. D. | en_US |
thesis.degree.name | Ph. D. | en_US |
thesis.degree.level | doctoral | en_US |
thesis.degree.grantor | Virginia Polytechnic Institute and State University | en_US |
thesis.degree.discipline | Aerospace Engineering | en_US |
dc.contributor.committeechair | Patil, Mayuresh J. | en_US |
dc.contributor.committeechair | Seidel, Gary D. | en_US |
dc.contributor.committeemember | Canfield, Robert Arthur | en_US |
dc.contributor.committeemember | Reich, Gregory W. | en_US |