X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 12 Apr 2008 10:41:24 -0400 Message-ID: X-Original-Return-Path: Received: from fmailhost01.isp.att.net ([204.127.217.101] verified) by logan.com (CommuniGate Pro SMTP 5.2.1) with ESMTP id 2844659 for lml@lancaironline.net; Sat, 12 Apr 2008 10:03:03 -0400 Received-SPF: pass receiver=logan.com; client-ip=204.127.217.101; envelope-from=dskeele@bellsouth.net Received: from fwebmail01.isp.att.net ([207.115.11.151]) by isp.att.net (frfwmhc01) with SMTP id <20080412140224H01004i6n6e>; Sat, 12 Apr 2008 14:02:24 +0000 X-Originating-IP: [207.115.11.151] Received: from [68.221.164.102] by fwebmail01.isp.att.net; Sat, 12 Apr 2008 14:02:23 +0000 From: dskeele@bellsouth.net X-Original-To: "Lancair Mailing List" Subject: Re: [LML] carbon-carbon composites Disposition-Notification-To: dskeele@bellsouth.net X-Original-Date: Sat, 12 Apr 2008 14:02:23 +0000 X-Original-Message-Id: <041220081402.21286.4800C0EF000185C90000532622218865869B0A02D2089B9A019C04040A0DBF0A040A0A059C0B@att.net> In-Reply-To: X-Mailer: AT&T Message Center Version 1 (Mar 10 2008) X-Authenticated-Sender: ZHNrZWVsZUBiZWxsc291dGgubmV0 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="NextPart_Webmail_9m3u9jl4l_21286_1208008943_0" --NextPart_Webmail_9m3u9jl4l_21286_1208008943_0 Content-Type: text/plain Content-Transfer-Encoding: 8bit Bob, Do you have a solution to a problem where the exhaust gasses exit the cowling area and have "chared " the epoxy airframe. I've seen this on a couple of LN-2's I've worked on, some others only just have discoloration of the paint in this area. Obviously, a solution was to move the exhault pipes down away from the fulislage, by either cutting and rewelding the tips, or shimming the system. Would a Carbon/Carbon or other high end "patch" etc be effective ?? Would appreciate your comments. Don Skeele A&P -------------- Original message from "bob mackey" : -------------- > > I think I missed something. > > What is carbon/carbon and what are the temp characteristics? > > Craig: > I'm glad you asked. Most of the previous replies on this subject > have been misinformed. > > Carbon (graphite fiber) retains its strength and stiffness well > up to about 2000 C. Yes... that's about 3600 degrees Fahrenheit. > It does start to oxidize at about 600 C (~1100 F) in air though, > so it is difficult to test to its full temperature range. > > Some have mentioned that "carbon composites" lose strength at > 120 F or some other low temperatures. Actually, the EPOXY softens > at temperatures varying with the type of epoxy. There is a wide > range, but typical values of Tg (glass transition temperature) > http://www.siliconfareast.com/tg.htm > are around 135 C. There are higher temperature resins like > phenolic or bis-maleimide with Tg of 200 C or more. > One of these days I'll rebuild my engine baffles with > carbon-bismaleimide composite instead of repairing the > cracked aluminum. > > > The highest temperature "resin" in common use is carbon itself. > Hence "carbon-carbon composite". That's carbon fibers with carbon resin, > forming a composite matrix. > http://www.composites-by-design.com/carbon-carbon.htm > The carbon resin can be pitch that is infiltrated into the carbon fiber > preform then fired to drive off the hydrogen. The pitch shrinks > leaving voids, so the process is repeated a few times. Other methods > use gas-phase carbon sources to carry the carbon into the matrix. > Because of the shrinkage, a final machining operation is often used > to make the net shape part. > > The end result is lighter and stronger than steel, and suitable for > use at extreme temperatures except for oxidizing flames. > Space shuttle re-entry tiles and many rocket engine nozzles are > made of C-C. > http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_sys.html > > If you want it to look metallic AND be made of lightweight > carbon-carbon, you could nickel-plate the carbon-carbon exhaust tunnels. :-) > > -bob mackey > > > > -- > For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html --NextPart_Webmail_9m3u9jl4l_21286_1208008943_0 Content-Type: multipart/related; boundary="NextPart_Webmail_9m3u9jl4l_21286_1208008943_1" --NextPart_Webmail_9m3u9jl4l_21286_1208008943_1 Content-Type: text/html Content-Transfer-Encoding: 8bit
Bob,
    Do you have a solution to a problem where the exhaust gasses exit the cowling area and have "chared " the epoxy airframe.  I've seen this on a couple of LN-2's I've worked on, some others only just have discoloration of the paint in this area. 
   Obviously, a solution was to move the exhault pipes down away from the fulislage, by either cutting and rewelding the tips, or shimming the system. 
   Would a Carbon/Carbon or other high end "patch" etc be effective ?? Would appreciate your comments.  Don Skeele   A&P 
-------------- Original message from "bob mackey" <n103md@yahoo.com>: --------------


> > I think I missed something.
> > What is carbon/carbon and what are the temp characteristics?
>
> Craig:
> I'm glad you asked. Most of the previous replies on this subject
> have been misinformed.
>
> Carbon (graphite fiber) retains its strength and stiffness well
> up to about 2000 C. Yes... that's about 3600 degrees Fahrenheit.
> It does start to oxidize at about 600 C (~1100 F) in air though,
> so it is difficult to test to its full temperature range.
>
> Some have mentioned that "carbon composites" lose strength at
> 120 F or some other low temperatures. Actually, the EPOXY softens
> at temperatures varying with the type of epoxy. There is a wide
> range, but typical values o f Tg (glass transition temperature)
> http://www.siliconfareast.com/tg.htm
> are around 135 C. There are higher temperature resins like
> phenolic or bis-maleimide with Tg of 200 C or more.
> One of these days I'll rebuild my engine baffles with
> carbon-bismaleimide composite instead of repairing the
> cracked aluminum.
>
>
> The highest temperature "resin" in common use is carbon itself.
> Hence "carbon-carbon composite". That's carbon fibers with carbon resin,
> forming a composite matrix.
> http://www.composites-by-design.com/carbon-carbon.htm
> The carbon resin can be pitch that is infiltrated into the carbon fiber
> preform then fired to drive off the hydrogen. The pitch shrinks
> leaving voids, so the process is repeated a few times. Other methods
> use gas-phase carbon sources to carry the carbon into the matrix.
> Because of the shrinkage, a final machinin g operation is often used
> to make the net shape part.
>
> The end result is lighter and stronger than steel, and suitable for
> use at extreme temperatures except for oxidizing flames.
> Space shuttle re-entry tiles and many rocket engine nozzles are
> made of C-C.
> http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_sys.html
>
> If you want it to look metallic AND be made of lightweight
> carbon-carbon, you could nickel-plate the carbon-carbon exhaust tunnels. :-)
>
> -bob mackey
>
>
>
> --
> For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html
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