High-performance composite materials exhibit both anisotropic strength
and stiffness properties. These anisotropic properties can be used to
produce highly-tailored aircraft structures that meet stringent
performance requirements, but these properties also present unique
challenges for analysis and design. New tools and techniques are
developed to address some of these important challenges. A
homogenization-based theory for beams is developed to accurately
predict the through-thickness stress and strain distribution in thick
composite beams. Numerical comparisons demonstrate that the proposed
beam theory can be used to obtain highly accurate results in up to
three orders of magnitude less computational time than
three-dimensional calculations. Due to the large finite-element model
requirements for thin composite structures used in aerospace
applications, parallel solution methods are explored. A parallel
direct Schur factorization method is developed. The parallel
scalability of the direct Schur approach is demonstrated for a large
finite-element problem with over 5 million unknowns. In order to
address manufacturing design requirements, a novel laminate
parametrization technique is presented that takes into account the
discrete nature of the ply-angle variables, and ply-contiguity
constraints. This parametrization technique is demonstrated on a
series of structural optimization problems including compliance
minimization of a plate, buckling design of a stiffened panel and
layup design of a full aircraft wing. The design and analysis of
composite structures for aircraft is not a stand-alone problem and
cannot be performed without multidisciplinary considerations. A
gradient-based aerostructural design optimization framework is
presented that partitions the disciplines into distinct process
groups. An approximate Newton--Krylov method is shown to be an
efficient aerostructural solution algorithm and excellent parallel
scalability of the algorithm is demonstrated. An induced drag
optimization study is performed to compare the trade-off between wing
weight and induced drag for wing tip extensions, raked wing tips and
winglets. The results demonstrate that it is possible to achieve a 43%
induced drag reduction with no weight penalty, a 28% induced drag
reduction with a 10% wing weight reduction, or a 20% wing weight
reduction with a 5% induced drag penalty from a baseline wing obtained
from a structural mass-minimization problem with fixed aerodynamic
loads.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OTU.1807/34078 |
| Date | 17 December 2012 |
| Creators | Kennedy, Graeme |
| Contributors | Martins, Joaquim R. R. A. |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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