High-Performance Structural Fibers for Advanced Polymer Matrix Composites (2005) / Chapter Skim
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4 Opportunities for DoD-Sponsored Research
4 Opportunities for DoD-Sponsored Research
Pages 36-49
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From page 36... ...
It can be expected that the development of multifunctional composites for armored vehicles, topside ship structures, and unmanned robotic and aerial vehicles will face similar demands to meet requirements for reduced weight and increased functionality. The creation of such composites will require prudent investment as well as vision on the part of DoD program managers.
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From page 37... ...
However, because of their graphitic structure, the thermal conductivities of pitch-based carbon fibers are as much as three times that of copper and orders of magnitude higher than those of PAN-based carbon fibers, and applications are now emerging in which heat transfer is critical. For example, management of excess heat has become a limiting factor in the design of many military aircraft, satellite structures, and electronic packages.
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From page 38... ...
Initiate fundamental studies for both PAN- and pitch-based carbon fibers to develop molecular orientation during flow, solidification, and heat treatment. Provide funding for new analytical methods such as MALDI that could lead to improved precursors for pitch-based carbon fibers and carbon-carbon matrices.
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From page 39... ...
. In addition, the use of carbon fiber with vinyl ester VARTM resins for ship structure requires additional study of sizings to
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From page 40... ...
Multifunctional composites can also provide the foundation for the integration of signature management, communication systems, power grids, and sensor arrays. It is recognized that the development of multifunctional composites for armored vehicles, topside ship structures, and unmanned robotic and aerial vehicles will require continuous DoD investment.
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From page 41... ...
is essential. Improved dimensional tolerance via materials and processing would provide a significant cost reduction in assembly and thus the use of composites.
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From page 42... ...
Although the concept of the building block approach is widely acknowledged in the composites industry, it is applied with varying degrees of rigor, and details are far from universal.4 This lack of standardization has hindered exploitation of the full potential of this approach. Ideally, a building block program is aimed at obtaining information at the lowest possible level of complexity and using analysis rather than testing as much as possible to minimize cost.
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From page 43... ...
Although these research thrusts carry a higher risk of failure than the nearer-term opportunities identified above, they would, if they are successful, produce dramatic performance gains for composite structures. Nanoscale Fibers Using current technology and precursors, only incremental improvements in fiber properties will be achieved.
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From page 44... ...
This leads to a helical arrangement of carbon atoms in the nanotube shells. Depending on the helicity and dimensions of the tubes, the electronic structure changes considerably.11,12 Hence, although graphite is a semimetal, carbon nanotubes can be either metallic or 7 Examples include Multidisciplinary University Research Initiatives (MURIs)
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From page 45... ...
The topology of nanotubes indicates extremely high thermal and electrical conductivity in the axial direction, and the measured longitudinal elastic modulus is in the terapascal range -- higher than that of any known material. The combination of high aspect ratio, small size, strength, stiffness, low density, and high conductivity makes nanotubes extremely intriguing candidates as fillers in polymer composites or in polymer precursors for graphite or aramid fibers.
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From page 46... ...
These should include more efficient processes for producing PAN, rather than the current wet-spinning technique, and exploring alternate methods that can decrease stabilization times and/or reduce the amount of oxygen added during stabilization and, thus, increase overall process conversion. Also, potentially low-cost precursor polymers with higher carbon contents should be evaluated.
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From page 47... ...
and alternate methods that can decrease stabilization times and/or reduce the amount of oxygen added during stabilization- and thus increase overall process conversion -- should be considered. Also, potentially low cost precursor polymers with higher carbon contents should be evaluated.
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From page 48... ...
However, next-generation materials will require new multiscale modeling methods to bridge the molecular interactions between constituents and the overall performance of the composite systems. It is also recognized that the processing science of multifunctional composites materials incorporating nanoscale constituents and devices must be developed.
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From page 49... ...
A carefully designed set of experiments is needed that would alter fiber properties, fiber strength distributions, interface properties (using some of the new interfaces developed in academia) , and matrix properties and then characterize the resulting interface behavior, as well as the macroscopic tensile, compressive, fatigue, creep, and toughness behavior as a function of each variable.
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