Re: Aircraft design question

Date:         27 Mar 2001 16:05:13 
From:         Malcolm Weir <malc@gelt.org>
Organization: Little to None
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On 23 Mar 2001 17:40:04 , "John R Weiss" <jrweiss98155@home.com> caused to
appear as if it was written:

>"Matthew Willshee" <matthew@amber-matt.freeserve.co.uk> wrote in message
>news:airliners.2001.42@ditka.Chicago.COM...
>> Dafydd ab Hugh <dafyddNO@SPAMsff.net> wrote in message
>> news:airliners.2001.3@ditka.Chicago.COM...
>
>> > There must be something out there; engineers build airplanes with
>> > passenger windows, so somebody knows how to design them!
>
>> The windows will probably be glass, which is a ceramic.
>
>Aircraft windshields are often made of laminates of acrylic and glass.
>Curved sections, like fighter canopies, are made of acrylic alone.
>
>I believe windows on deep submersibles have been made of quartz.

Actually, no.

Deep submersibles (e.g. the Trieste, which hold the record for the deepest
dive ever, and one that won't be exceeded without a shovel!) use plexiglass.

The reason is as another poster stated: ceramics don't have a failure limit,
they have a probability function.

Plexiglass, by contrast, "cold flows" under enormous pressure.  So
undetectable flaws "heal" rather than rupture.

But the bottom line is that Piccard (the man who deisgned and built the
Triest) used plexiglass for that vessel, and the problems facing submersible
are different: huge pressure, low hear.  Aircraft face high temperatures,
and trivial pressure (14.7psi vs ~90,000psi, IIRC, at 20,000 feet below sea
level).

Malc.