Martin Ling wrote:
> On Tue, Aug 08, 2000 at 12:48:21AM -0400, John Clark wrote:
> > Martin Ling <martin@nodezero.org.uk> asks about strong materials:
> >
> > Sapphire whiskers (Al2O3) is the strongest material that has been
> > measured, a cable 2 inches across could support 10,000 tons.
>
> Thanks - checking that out now.
>
> > Carbon nanotubes (bucky tubes) are almost certainly stronger but to
> > my knowledge a precise strength measurement hasn't been made.
> > Theoretically the strongest of all could be C3N4 if somebody could
> > make some, but nobody has yet.
>
> Are there rough figures/estimates for either of these (basically, I just
> need order of magnitude)?
Here is a table of some rough tensile strengths (real and theoretical) and
a list of my sources. I couldn't find anything on Aluminum Whiskers,
although I know I've seen a table on the Web that included them once.
IIRC, they have a higher tensile strength than carbon whiskers, but are
more than proportionately denser, making them an inferior choice for this
sort of application:
Todays Best Carbon Fiber: 6.9 Gpa [1]
Outer wall of Multi-walled BuckyTube: 63 Gpa [2]
Aluminum (cold formed) .36 Gpa 2,650 Kg/m^3 [3]
Steel (cold drawn) 1.24 Gpa 7,800 Kg/m^3 [3]
Titanium (cold formed) .93 Gpa 4,540 Kg/m^3 [3]
Graphite crystals 21 Gpa 2,200 Kg/m^3 [3]
Diamondoid 50 3,510 Kg/m^3 [3]
Thornel T-40 (Carbon Fiber) 5.65 Gpa 1,810 Kg/m^3 [4]
Spectra-2000 (plastic) 3.25 GPa 970 Kg/m^3 [4]
Steel 4.22 GPa 7,850 Kg/m^3 [4]
Theoretical Strength of Buckytubes : 200 Gpa [5]
[1] <http://home.att.net/~ederd/canon.html>
[2] <http://www.eurekalert.org/releases/wusm-mmm013100.html>
[3] <http://www.zyvex.com/nanotech/nano4/mckendreePaper.html#RTFToC7>
[4] <http://www.spacefuture.com/archive/space_elevators_space_hotels_
and_space_tourism.shtml>
[5] I've found many references claiming to have heard this number
somewhere authoritive, but I've yet to find any authority who
would claim this.
I should also mention that, according to [1], a reasonable space tether
design requires a minimum of 12.5 GPa tensile strength.
--
Stirling Westrup | Use of the Internet by this poster
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