Title page for ETD etd-07282008-134754
|Type of Document
||Optimal design of geodesically stiffened composite cylindrical shells
|Griffin, Odis Hayden Jr.
|Haftka, Raphael T.
|Johnson, Eric R.
|Mook, Dean T.
|Reddy, Junuthula N.
|Date of Defense
An optimization system based on the finite element code CSM Testbed and the optimization
program ADS is described. The optimization system can be used to obtain
minimum-weight designs of composite stiffened structures. Ply thicknesses, ply orientations,
and stiffener heights can be used as design variables. Buckling, displacement,
and material failure constraints can be imposed on the design. The system is used to
conduct a design study of geodesically stiffened shells. For comparison purposes, optimal
designs of unstiffened shells and shells stiffened by rings and stringers are also
obtained. Trends in the design of geodesically stiffened shells are identified. An approach
to include local stress concentrations during the design optimization process is
then presented. The method is based on a global/local analysis technique. It employs
spline interpolation functions to determine displacements and rotations from a global
model which are used as "boundary conditions" for the local model. The organization
of the strategy in the context of an optimization process is described. The method is
validated with an example.
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