Re: [ATM] Carbon Fiber and aluminum

[artbianconi@blast.net]

Haven't a clue Roger but I suspect that the wings and attachments 
on the Shuttle are not stressed for loads anywhere near what an 
F16 fighter is. Not in positive G's and most certainly not in 
negative G's. In fact I'll guess that the wings on a Pitts S1S or 
Laser are stressed for much higher loads than either the Shuttle 
or the F-16 due to the aerobatic nature of those aircraft.

Just so you are clear on this, the failure that occurred on the 
shuttle was due to extreme over-heating of the internal primary 
structural materials from a "blowtorch" in the leading edge. The 
same type of friction that makes meteorites burn and which make 
the titanium leading edges of the X-15 and S-7 Blackbird glow 
bright orange. They did not fail because of any galvanic 
reaction. That much I can say with some degree of certainty.

None of these are going to be factors in a nine pound 6" 
telescope that rotates at best, 180 degrees once every 12 hours

Art Bianconi


> Back to the drawing board...  
> 
> But how do (or did) the shuttle wings manage?
> 
> Roger
> 
> ----- Original Message ----- 
> From: <artbianconi@blast.net>
> To: <atm@atmlist.net>
> Sent: Sunday, August 08, 2004 10:01 AM
> Subject: [ATM] Carbon Fiber and aluminum
> 
> 
> > I've been away from hands-on fabrication of composite parts
> > using Carbon Fiber. A lot can happen in two years so I did 
some
> > homework. I discovered that the threaded aluminum inserts in 
my
> > carbon fiber truss tubes don't get along with carbon fiber at
> > all! Galvanic erosion will attack the aluminum at the 
interface
> > of the two materials and turn it to dust. And, if there is 
any
> > water present, the destruction of the mechanical bond will be
> > rapid.
> > 
> > I bounced this discovery off a few aerospace engineers I know
> > and they confirmed my worst fears. One wrote back:
> > 
> > "Carbon Fiber does indeed attack aluminum 
> > VORACIOUSLY if any hint of moisture gets into 
> > the matrix.  All the metal parts on the F-16 fighter that
> > contact CF are Stainless Steel,  Passivated too if I am not
> > mistaken to more closely match the electronegativity value of
> > the two materials."
> > 
> > If you propose to develop an OTA using carbon fiber, be 
certain
> > that your choices of metals and fasteners are CF tolerant,  
or
> > insulate them first from direct contact with an intermediary
> > layer of fiberglass
> > 
> > Art Bianconi
> > 
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> > 
> > 
> > 
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