Great point. Thanks for digging this up. Before that, I was trying to figure out what would be serving as a cathode in that bonding. The dope slap was Boeing's table embedded in the article you referenced. I was visualizing the carbon fiber as embedded in the more-or-less insulating epoxy resin. [Slap!] http://www.boeing.com/commercial/aeroma ... ble01.htmlLance Murray wrote:The root cause of this issue is that you should not bond carbon and aluminum together. This was an idiotic design failure. "Fiber-reinforced plastics are corrosion resistant, but plastics reinforced with carbon fibers can induce galvanic corrosion in attached aluminum structure."
Corrosion within the laminate
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- rwtucker
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Re: Corrosion within the laminate
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Re: Corrosion within the laminate
I don't believe that there is any carbon fiber in the area in question.
Steve
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Re: Corrosion within the laminate
It sounds like the potential for galvanic corrosion might be a bigger issue for DA42s than DA40s, since the DA40 only has a small amount of carbon fiber (CFRP), including the "roll cage" around the cockpit, and parts of the wing spars. Otherwise everything is fiberglass (GFRP).
In contrast the DA42 has more carbon fiber than fiberglass, including carbon fiber engine cowlings, wings, and fuselage/tail. The only large fiberglass surface on the DA42 is the rear horizontal stabilizer.
While not as old as steam-gauge DA40s, early DA42s will soon be more than a decade old.
In contrast the DA42 has more carbon fiber than fiberglass, including carbon fiber engine cowlings, wings, and fuselage/tail. The only large fiberglass surface on the DA42 is the rear horizontal stabilizer.
While not as old as steam-gauge DA40s, early DA42s will soon be more than a decade old.
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Former DA40XLS, DA42-VI, and DA62 owner
ATP, CFI, CFI-I, MEI
Former DA40XLS, DA42-VI, and DA62 owner
ATP, CFI, CFI-I, MEI
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Re: Corrosion within the laminate
Copper?Steve wrote:I don't believe that there is any carbon fiber in the area in question.Steve
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Re: Corrosion within the laminate
Actually, I went home and looked at the AMM tonight. There are actually areas of carbon fiber in both the top and bottom of the wing, but the diagrams are not sufficiently detailed for me to determine if it is in the grounding strap area. The fuselage center section adjacent to the wing does not show any carbon fiber laminae.rwtucker wrote:Copper?Steve wrote:I don't believe that there is any carbon fiber in the area in question.Steve
Steve
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Re: Corrosion within the laminate
This corrosion is not carbon-only related. As any boat owner will tell you, once the composite is penetrated and not sealed the composite will start to delaminate due to water intrusion. If you drill a hole through composite you are supposed to seal the inner surface of that hole with polyester/epoxy/some other sealer - this is not done in any hole that I have seen in the Diamonds. Composite aircraft that are left outside fair far worse than hangared airplanes, but even hangared planes will suffer water intrusion related delamination over time. Where you have metal in the composite, that just means it will start to corrode even in ambient air - no water intrussion required. If you have a composite sandwich, then put an aluminum mesh in the composite, then bond carbon in the composite, then put a bolt of dissimilar metal through all of that, then throw in water or moisture, then vibrate it on a regular basis, you are going to get corrosion, delamination, electrolysis - all kinds of problems.
This issue is an inherent design flaw in most composite GA aircraft. I wonder how Boeing and Airbus address this in the composite parts of their aircraft - not just the 787 and A350. They have been using composite parts for decades.
This issue is an inherent design flaw in most composite GA aircraft. I wonder how Boeing and Airbus address this in the composite parts of their aircraft - not just the 787 and A350. They have been using composite parts for decades.
Last edited by ihfanjv on Sat Aug 08, 2015 5:07 pm, edited 1 time in total.
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Re: Corrosion within the laminate
Somewhere on this site or the competitive site someone detailed the repair process with photos and if I remember correctly this area is carbon directly bonded to an untreated aluminum strip at the root. Yes it is drilled through giving a direct path for an electrolyte to pass giving all the elements of a battery.
In fact every piece of aluminum I have found on my airplane is untreated.
In fact every piece of aluminum I have found on my airplane is untreated.
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Re: Corrosion within the laminate
Does anyone remember where the detailed repair process was illustrated? I remember seeing it but am unable to find it.
Thanks!
Keith
Thanks!
Keith
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Re: Corrosion within the laminate
The best picture I have ever seen is the one from the first post in this thread which had been provided to me by Diamond.
I decided to get the work done last year at XU Aviation in London ON. A flawless job. Given that it involved grinding all around the section of the wing (top and bottom) along the bonding strip, redoing the layup and fairing, and repainting the entire wing, I thought it was relatively inexpensive. And it fixed the badly chipped leading edge at the same time. The only unexpected thing in the repair was that several flap and aileron hinges could not be taken apart due to corrosion and had to be replaced.
The guys at XU have done more than a few of those and it showed in the speed and quality of the work they did on my plane.
I decided to get the work done last year at XU Aviation in London ON. A flawless job. Given that it involved grinding all around the section of the wing (top and bottom) along the bonding strip, redoing the layup and fairing, and repainting the entire wing, I thought it was relatively inexpensive. And it fixed the badly chipped leading edge at the same time. The only unexpected thing in the repair was that several flap and aileron hinges could not be taken apart due to corrosion and had to be replaced.
The guys at XU have done more than a few of those and it showed in the speed and quality of the work they did on my plane.
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Re: Corrosion within the laminate
Well, it looks like my 2002 DA40 - with 800 hrs - and has always been hangered at KLOM (Wings, NE of Philly) has joined the club of DA40' requiring repair work to address this laminate/corrosion problem.
While doing a pre-annual walk around with Wing's Head of Maintenance to discuss my aircraft's squawks and the process of conducting the major structural inspection and bonding test we found this issue on both wings. As my A&P tapped the wing with a quarter you could really hear the change in sound as he tapped toward the suspect area.
Has anyone recently had this work done on their DA40/42? If so where and what were the cost of repairs? Thanks
On a tangential note: This was already going to be a big maintenance budget year as I have a new MT prop that should be delivered prior to the annual. Aside from the old prop's cosmetics and the fact the aircraft's first owner never had the prop overhauled the prop has served me well these past two years. But in an overabundance of caution I decided to go with a new prop before problems surfaced. I just did not want to deal with a prolonged down time waiting for a new prop.
While doing a pre-annual walk around with Wing's Head of Maintenance to discuss my aircraft's squawks and the process of conducting the major structural inspection and bonding test we found this issue on both wings. As my A&P tapped the wing with a quarter you could really hear the change in sound as he tapped toward the suspect area.
Has anyone recently had this work done on their DA40/42? If so where and what were the cost of repairs? Thanks
On a tangential note: This was already going to be a big maintenance budget year as I have a new MT prop that should be delivered prior to the annual. Aside from the old prop's cosmetics and the fact the aircraft's first owner never had the prop overhauled the prop has served me well these past two years. But in an overabundance of caution I decided to go with a new prop before problems surfaced. I just did not want to deal with a prolonged down time waiting for a new prop.