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From: Bruce_Dunn@mindlink.UUCP (Bruce Dunn)
Newsgroups: sci.space
Subject: Kevlar (was:  Manoeuvring using rope and anchor)
Message-ID: <4728@mindlink.UUCP>
Date: 8 Feb 91 02:02:56 GMT
Organization: MIND LINK! - British Columbia, Canada
Lines: 34

> gregc@cimage.com writes:
> Person: Greg Cronau
> 
> I don't even want to *think* about the number of G's on the spacecraft
> when that sucker goes taunt. You'd have to make the cable out of something
> resilient so that it would stretch to absorb the initial shock.
> You could make the cable out of a kevlar bungee. Certainly would give a
> new meaning to the concept of a "slingshot" manuever. :-)
> 
> gregc@cimage.com


     Kevlar is fascinating stuff.  I just acquired a spool of Kevlar fiber for
tinkering purposes.  It looks like pale yellow dental floss, or like polyester
sewing thread.  The spool that I have is loaded with a strand that has two
individual thread-like fiber bundles twisted around each other.  The thread is
quite flexible in spite of the very high Young's modulus of the fiber (high
stiffness).  This is probably because the actual fibers making up the thread
are extremely fine (nearly invisible if the end of a thread is frayed out), and
the thread can bend by flexing of the fibers over one another.
     The real surprise comes when you cut off a length of fiber and try to
break it by hand.  You can't exert enough force with your bare hands to break
the fiber (at least not without risking having the fiber cut into your flesh).
What looks like a thread has the tensile strength of steel wire roughly the
same thickness.
     The Kevlar I bought was obtained from the Canadian distributor for Edmond
Scientific.  In the Edmond catalog, the item is catalog number G34,883.  Price
is $13.50 U.S. for a 600 yard spool.

     I don't have the contact information for Edmond Scientific in the U.S.,
but Canadians may contact Eftonscience Inc., 3350 Dufferin St., Toronto
Ontarion M6A 3A4  (416-787-4581).
--
Bruce Dunn   Vancouver, Canada    a752@mindlink.UUCP