Space elevator will be built around 2015

Keith F. Lynch wrote:
is it possible to simply cause the carbon nanotubes to branch and
mesh? Or perhaps to form into interlocking loops?

Geoffrey A. Landis wrote:
The current issue of _NASA Tech Briefs_ has an article about the
electronic theory of branched carbon nanotubes, including some
nice graphics.

Thanks. I see that _NASA Tech Briefs_ is online, but I can't find
that article. Do you have the exact URL?

So far nobody has responded to my interlocking loops suggestion.
Even if carbon nanotubes only have their full strength when they don't
branch, I doubt a sufficiently gentle radius of curvature would make
a difference, unless they have little *sideways* strength. Note
that by constructing bundles of millions of parallel fibers, perhaps
resembling a bicycle tire in shape and size (and color?), you can
get the radius of curvature as low as you like even if each "tire"
interlocks with other "tires," and they're all under tremendous stress.
--
Keith F. Lynch - - http://keithlynch.net/
I always welcome replies to my e-mail, postings, and web pages, but
unsolicited bulk e-mail (spam) is not acceptable. Please do not send me
HTML, "rich text," or attachments, as all such email is discarded unread.

Keith F. Lynch wrote:
Webmasters will miss out on a lot of high quality readers if they
insist on using proprietary formats instead of HTML for their pages.
There are *billions* of other pages I can view. I'm not going to
waste time on the format-of-the-month-club.

George William Herbert wrote:
I am sorry, but insisting that you reach at least 1992 technology
to participate in the modern web is probably not unreasonable.

"Anyone who slaps a 'this page is best viewed with Browser X' label
on a Web page appears to be yearning for the bad old days, before
the Web, when you had very little chance of reading a document
written on another computer, another word processor, or another
network." -- Tim Berners-Lee, inventor of the web

Sounds like you're the one yearning for the past. In 1992 it looked
like platform independence was right around the corner. Like fusion
energy and inexpensive space travel, it's still just around the corner.

There's not much I can do to bring about practical fusion or
inexpensive space travel, but I can and do work for platform
independence. All of my web pages are platform independent. Any text
on them can be viewed by anyone with hardware capable of displaying
text. I don't care if it's an ASR33 teletype built in the 1960s,
or a ten megapixel 19 inch monitor built last Tuesday. And I don't
frequent sites that tell me to go away until I have "upgraded" to
something proprietary to Microsoft or Adobe or AOL or anyone else.

It's not like I am in any danger of running out of interesting sites
I can view with my VT420 terminal. I couldn't read them all in a
thousand years, even if I did nothing else, and even if nobody added
any new pages.
--
Keith F. Lynch - - http://keithlynch.net/
I always welcome replies to my e-mail, postings, and web pages, but
unsolicited bulk e-mail (spam) is not acceptable. Please do not send me
HTML, "rich text," or attachments, as all such email is discarded unread.

Finding a matrix that will bond reasonably well to nanotubes turns
out to be difficult; nanotubes are quite slippery and don't bond well to much
of anything.
Actually, there's no need for reinforcement to "bond" to the mixture it's
reinforcing. Look at rebar in concrete and glass fibers in epoxy plastic.
they're not strongly bonded, just fixed in place and then become mechanically
integral.
Nanotubes are going to happen, just as soon as an industry takes them beyond
the college lab. And they will, there's always a market for stronger fibers.
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

Allen Meece wrote:
Finding a matrix that will bond reasonably well to nanotubes turns
out to be difficult; nanotubes are quite slippery and don't bond well to much
of anything.
Actually, there's no need for reinforcement to "bond" to the mixture it's
reinforcing. Look at rebar in concrete and glass fibers in epoxy plastic.
they're not strongly bonded, just fixed in place and then become mechanically
integral.

Um. Allen? Read up some on composites.

Stick a single glass fiber in a paper cup full of mixed epoxy.
Try to pull it out after it hardens.

Try the same thing with rebar and a bucket of cement.

Even better, try the same thing with a smooth steel rod embedded in cement.


-george william herbert

In article ,
Allen Meece wrote:
Actually, there's no need for reinforcement to "bond" to the mixture it's
reinforcing. Look at rebar in concrete and glass fibers in epoxy plastic.
they're not strongly bonded, just fixed in place and then become mechanically
integral.

Ever wonder why rebar has that funny textured surface? It's to improve
(mechanical) bonding to the concrete, which otherwise would be inadequate.
The glass fibers in glass-epoxy typically have non-trivial surface
coatings to improve adhesion. And these are materials which are not
naturally slippery.

There is most definitely a need for the fibers to bond to the matrix.
Moreover, the bond has to have the right strength -- not too loose, not
too strong. (Yes, "not too strong". You want the bond to fail before the
fiber does, so that the material fails by pulling the fibers out of the
matrix rather than by propagating cracks through the fibers, because the
former requires much more energy.)

You might want to learn a bit more about composite materials before
sounding off on this. J.E. Gordon's "The New Science of Strong Materials"
is a good gentle introduction to such topics (and despite being a bit old
and written for a popular audience, it still sees use as an engineering
textbook).

Nanotubes are going to happen, just as soon as an industry takes them beyond
the college lab.

They are already beyond the college lab... for applications not requiring
strength. In particular, quite a small percentage of even quite short
nanotubes mixed in with plastic make the plastic slightly electrically
conductive, and *that* has major industrial applications, because it means
you can use electrostatic painting and coating processes on such plastics.
(Other ways of rendering plastics conductive typically require much larger
percentages of additives, which adversely affect other properties.)
Commercial production is imminent.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

"George William Herbert" wrote in message
...
Allen Meece wrote:
Finding a matrix that will bond reasonably well to nanotubes turns
out to be difficult; nanotubes are quite slippery and don't bond well
to much
of anything.
Actually, there's no need for reinforcement to "bond" to the mixture
it's
reinforcing. Look at rebar in concrete and glass fibers in epoxy plastic.
they're not strongly bonded, just fixed in place and then become
mechanically
integral.

Um. Allen? Read up some on composites.

Stick a single glass fiber in a paper cup full of mixed epoxy.
Try to pull it out after it hardens.

Try the same thing with rebar and a bucket of cement.

Even better, try the same thing with a smooth steel rod embedded in
cement.

I remember my Materials Science lecturer at University talking about the
promise that ceramic fibres had shown in the lab over the previous few
years, when they had managed to produce 1mm long ceramic fibre. It was
*going* to revolutionise everything.

Sadly once you tried to make a fibre longer than that the structure
collapsed due to poorly understood material issues.

I have concerns about this "in a bound they were free" approach to the
practicalities of nano-tubes.

I hope they live up to promise, but I'm not betting on it.

Dave wrote:
I remember my Materials Science lecturer at University talking about the
promise that ceramic fibres had shown in the lab over the previous few
years, when they had managed to produce 1mm long ceramic fibre. It was
*going* to revolutionise everything.

Sadly once you tried to make a fibre longer than that the structure
collapsed due to poorly understood material issues.

Have you heard of Nextel fiber? 8-)

http://www.3m.com/market/industrial/...s/nextel.jhtml


-george william herbert

"George William Herbert" wrote in message
...
Dave wrote:
I remember my Materials Science lecturer at University talking about the
promise that ceramic fibres had shown in the lab over the previous few
years, when they had managed to produce 1mm long ceramic fibre. It was
*going* to revolutionise everything.

Sadly once you tried to make a fibre longer than that the structure
collapsed due to poorly understood material issues.

Have you heard of Nextel fiber? 8-)

http://www.3m.com/market/industrial/...s/nextel.jhtml

Ah, ok, but that wasn't quite what we were talking about in those halycon
days of the mid 80s' ;-)