High Temperature Irradiation of 3D CC

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High Temperature Irradiation of 3-D C/C
Composite in Support of Laser IFE Lance L
Snead Timothy D Burchell Oak Ridge National
Laboratory
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SOMBRERO is the starting-point design, though
the conceptual design effort currently
underway may substantially alter the design
point. Temperature range is currently
assumed to be 600-1500C. Chamber
environment, hence surface particle flux and
energy is unknown.
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Sombrero Useful lifetime assumed based on
existing graphite literature
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Irradiation Induced Dimensional Change in
Advanced CFCs
Interstitials created during irradiation form
new graphitic basal planes leading to highly
anisotropic dimensional changes. Engineering
composites can balance and minimize such
dimensional changes There are no very high
temperature data on 3 dimensional CFCs.
1000C, 10 dpa
Oku Data
NRL IFE 2/2001
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Radiation stability of graphite fibers in
composites
Unidirectional Fiber Composite
Graphite fiber composites first gain strength
(lt few dpa) then rapidly lose strength as c-axis
expansion causes widespread microcracking
Fiber can be expected to shrink axially and
swell radially putting interface under
tension. Unidirectional composite will
undergo large anisotropic swelling, eventually
causing composite disintegration.
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Materials and Irradiation
500 and 800C, HFIR irradiation to 10 dpa
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Flexure Curves
Poco AXF-5Q Graphite
3-D FMI-222 Comppsite
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Results
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Fiber Bundle Length Shrinkage
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Fiber Bundle Diameter Swelling
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Balancing Radiation-Induced Dimensional Change
Gross dimensional change occurs, though
composite retains strength and does not enter
into swelling regime.
10 dpa
500C
gap
800C
sample surface
bundle swelling
bundle shrinkage
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Conclusion
This study has shown that, for a very high
quality, balanced weave carbon fiber composite
FMI-222, irradiation-induced increase in
fracture strength is retained in the anisotropic
swelling regime generally associated with severe
loss in strength. This has been demonstrated by
comparison of the standard isotropic graphite
Poco AXF-5Q and the balanced weave pitch-based
fiber composite FMI-222. At the highest dose and
temperature, 7.7 x 1025n/m2 and 800C, the
graphite material was seen to undergo swelling
with an associated 13 decrease in strength,
while the composite material exhibited a 37
higher strength. Even though the material had
entered into the swelling regime the 3-D
architecture compensated for these changes,
extending its useful lifetime.