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To quantify the weight
savings of advanced composites the chart below compares various
metals and various advanced composite fabrication methods &
materials. The chart below shows the weights of given materials
to yield roughly the same strength irregardless of the material,
yet their weights are vastly different. |
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stainless steel |
30lbs |
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aluminum |
15lbs |
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solid E-glass (fiberglass) |
15lbs |
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solid carbon fiber |
9lbs or less |
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Kevlar skinned honeycomb
core |
3lbs or less |
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carbon fiber skinned honeycomb core |
2.5lbs or less |
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Weight savings is one
of the key advantages of using advanced composites. The second
main advantage in using advanced composites is that the CTE (coefficient
of thermal expansion) can be minimized. The chart below shows
CTE figures of different materials. |
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Nomex honeycomb core |
20 |
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magnesium |
14.6 |
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aluminum (2024, 6061, etc.) |
~13 |
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brass |
~11 |
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copper |
~10 |
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stainless steel (303 to 403) |
5.5-9.7 |
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gold |
8.2 |
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E-glass (fiberglass) |
7-8 |
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steel |
6.5-7.5 |
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nickel |
7.4 |
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titanium |
4.8-5.6 |
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zirconium |
3.2 |
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Kevlar |
3 and lower |
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carbon fiber - basic woven material |
2 and lower |
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invar |
1.6 and lower |
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specialized composite materials |
~0 |
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unidirectional carbon fiber |
slight negative (longitudinal) |
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All figures listed above
are in inch/inch degree F. |
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All of the materials listed above can be produced
in a variety of ways. Those variations each have their own specific
CTE. Thus the chart above is a rough reference for CTE's of different
materials. In reality material properties are much more complex
than the chart implies. For example, carbon fiber can have a
broad range of CTE's, say -1 to 8+, depending on the direction
measured, the fabric weave utilized, whether the material was
produced from Pan based (high strength, higher CTE) or Pitch
based (high modulus/stiffness, lower CTE), etc.. |
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Minimizing the expansion/contraction
is a prime objective as it can influence much more than just
focus: optical spacing, collimation, etc.. Advanced composites
can be chosen that not only reduce weight but also optimize CTE. |
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To learn more about advanced
composites, click here. |
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