Title page for ETD etd-09082012-040520
|Type of Document
||Knott, Tamara Wright
||Effect of fiber morphology on composite properties
||Master of Science
|Herakovich, Carl T.
|Griffin, Odis Hayden Jr.
|Pinders, M. Jeff
|Date of Defense
The effect of the cylindrically orthotropic morphology known to exist in graphite fibers on the effective properties of a composite material was studied using the composite cylinder
assemblage model. The cylindrical orthotropy of the fibers was found to have no effect on the
properties of a composite with purely orthotropic fibers. For fibers with a transversely
isotropic core both the size of the core and the morphology of the sheath were found to have
an effect on the composite properties.
The stress states resulting in the composite cylinder for axiai, radial, axiai shear, and thermal
loads were examined. Singular stresses were observed to occur at r=0 in some fibers in
some load conditions. The presence of a transversely isotropic core, which must exist in a
real fiber, removed this singularity.
The strength of the composite cylinder was found to depend on über morphology. The size
of the transversely isotropic core within the über also affected the strength. The strength of
the über increased with increasing transversely isotropic core size in some instances. In
general, for axiai loading failure is expected to be caused by fiber breakage. For radial, axiai
shear, and thermal loading the failure mode is über splitting.
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