Title page for ETD etd-07282008-134249
|Type of Document
||Kassegne, Samuel Kinde
||Layerwise theory for discretely stiffened laminated cylindrical shells
|Reddy, Junuthula N.
|Hendricks, Scott L.
|Plaut, Raymond H.
|Telionis, Demetri P.
|Date of Defense
The Layerwise Shell Theory is used to model discretely stiffened laminated composite
cylindrical shells for stress, vibration, pre-buckling and post-buckling analysis. The
layerwise theory reduces a three-dimensional problem to a two-dimensional problem by
expanding the three-dimensional displacement field as a function of a surface-wise two-dimensional
displacement field and a one-dimensional interpolation through the shell
thickness. Any required degree of accuracy can be obtained by an appropriate,
independent selection of the one-dimensional interpolation functions through the
thickness and the two-dimensional interpolation of the variables on the surface.
Using a layerwise format, discrete axial and circumferential stiffeners are modeled as
two-dimensional beam elements. Similar displacement fields are prescribed for both the
stiffener and shell elements. The contribution of the stiffeners to the membrane
stretching, bending and twisting stiffnesses of the laminated shell is accounted for by
forcing compatibility of strains and equilibrium of forces between the stiffeners and the
shell skin. The layerwise theory is also used to model initial imperfections of the
unstressed configuration. A finite element scheme of the layerwise model is developed
and applied here to investigate the effect of imperfections on the response of laminated
Using a finite element model of the layerwise theory for shells and shell stiffener
elements, the accuracy and reliability of the elements is investigated through a wide
variety of examples. The examples include laminated stiffened and unstiffened plates
and shells and stand-alone beams under different types of external destabilizing loads.
Finally, the study identifies the particular types of problems where the layerwise elements
possess a clear advantage and superiority over the conventional equivalent single-layer
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