bonding 2 pieces of ali?
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Thanks Max. As you have probably guessed I use these at work. I dont know the exact formulation of the silanes we use as the manufacturers are very secretive about their chemistry. I do know that they seem to work with most metals, ceramics and resins. They are extremely technique sensitive too. ANY deviation from the approved technique will fail. Not grit blasting metal/ceramic WILL fail. The 'glue' is far less important than the surface treatment but the correct technique for the particular material is vital. I have many successful silane bonded metallo-ceramics up to 20 years old in perhaps the most demanding environment.
Pop rivets? Yeah I use those too. Not in people's heads though.
A few years ago I was witness to an engineer (now no longer with us) treating a trailing edge main rotor blade delamination to a quick slap of some stuff with "Bell Helicopter" written on the tube. Needless to say by the next annual the 'bond' had failed.
Pop rivets? Yeah I use those too. Not in people's heads though.
A few years ago I was witness to an engineer (now no longer with us) treating a trailing edge main rotor blade delamination to a quick slap of some stuff with "Bell Helicopter" written on the tube. Needless to say by the next annual the 'bond' had failed.
Last edited by Gaseous; 3rd May 2009 at 21:57. Reason: typo
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treating a trailing edge main rotor blade delamination to a quick slap of some stuff with "Bell Helicopter" written on the tube.
as I said before, correct prep and priming is the key......Ithink we're all agreed on that,- as an aside, "araldite" is only one type of epoxy,among many made by the same company ( Ciba-Geigy, IIRC) other companies will have competing product -lines. Universal adhesives are not likely to be as good as an application-specific one.
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Rivets???
You are right DS. Provided tracker69 gave the joint a decent overlap, then almost any adhesive should provide a joint that will be stronger than the metal. Do not use average shear strength to design the overlap. Lap-shear strength quoted in data sheets is a meaningless parameter. As a broad rule of thumb, the overlap needs to be 30t for a double sided joint and 50t for a single sided joint.
For 0.032 2024 T3 that joint should carry over 2000 lbs. If you rivet it, I guess that you would not even get near to 1500 lbs. Glue it, don't screw it!
For 0.032 2024 T3 that joint should carry over 2000 lbs. If you rivet it, I guess that you would not even get near to 1500 lbs. Glue it, don't screw it!
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Gaseous, I noted your comment:
How many aircraft repair manuals contain such procedures? Or worse yet, injection repairs where you drill holes in a sandwich panel and inject adhesive. Given that to get a bond the surface must be clean AND chemically active, you can never achieve thse conditions either by lifting an edge or by drilling holes. You only ever get two things out of injection repairs; 1. you fill the air gap so that if you tap it it sound as if it is bonded, and 2. you get a warm fuzzy feeling that you have done something. Structurally, you have achieved dead set zero. Such processes can never achieve even minimal bond strength. The surfaces are not chemically active and may be contaminated anyway, so there is absolutely no way chemical bonds can occur at the interface.
It is in fact better to just paint the skin at the disbond bright pink. This has many advantages:
1. Everyone knows that the component is disbonded.
2. It takes less time next inspection to find the disbond.
3. If you are careful in painting the area, you can actually monitor if the disbond grows.
4. You haven't penetrated the panel so moisture is kept out.
5. The additional paint provides corrosion protection.
Structurally, the results are exactly the same.
I have seen cases where structural failures occurred because of injection repairs and large components (up to 12 ft x 8 ft) departed the aircraft. I have seen rudders fail in flight because of injection repairs implemented during production.
It really is time that these repairs are prohibited. The organisation I worked for actually did prohibit them but with every new aircraft type acquired, there are the same old injection repairs in the manuals. Why do the regulators permit manufacturers to use these processes without any validation testing?
I defy anyone to show me test results (other than just NDT) which show any shred of evidence that injection repairs achieve anything!!!
A few years ago I was witness to an engineer (now no longer with us) treating a trailing edge main rotor blade delamination to a quick slap of some stuff with "Bell Helicopter" written on the tube. Needless to say by the next annual the 'bond' had failed.
It is in fact better to just paint the skin at the disbond bright pink. This has many advantages:
1. Everyone knows that the component is disbonded.
2. It takes less time next inspection to find the disbond.
3. If you are careful in painting the area, you can actually monitor if the disbond grows.
4. You haven't penetrated the panel so moisture is kept out.
5. The additional paint provides corrosion protection.
Structurally, the results are exactly the same.
I have seen cases where structural failures occurred because of injection repairs and large components (up to 12 ft x 8 ft) departed the aircraft. I have seen rudders fail in flight because of injection repairs implemented during production.
It really is time that these repairs are prohibited. The organisation I worked for actually did prohibit them but with every new aircraft type acquired, there are the same old injection repairs in the manuals. Why do the regulators permit manufacturers to use these processes without any validation testing?
I defy anyone to show me test results (other than just NDT) which show any shred of evidence that injection repairs achieve anything!!!
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Lap shear
DS, It is even mor horrifying to know that 76% of US manufacturers still use an average shear stress design approach (FAA Workdshop Seattle 2004). 
This must be backed up by a plethora of tests at coupon, detail, element, subcomponent and component tests. If they designed using Hart-Smith's equations to calculate the load capacity of the adhesive and then designed the joint to achieve that load capacity then every adhesive joint would NEVER fail. Every coupon..... etc. test would break the metal, so you could reduce the number of tests by an order of magnitude, thus saving millions on certification costs. As well as that materials substitution requires a simple calculation to show equivalent joint strength. In the current method, a complete substantiation program may be necessary.
If the same approach was used for repair design and that was combinded with reliable validation of bonding processes, then such repairs would never fail, thus reducing maintenance costs.
I know of one repair on a 777 TE flap that has been repeated by a repair station crew four times. You'd think that they would relaise that there is a problem.
The real root of the problem is that the FARs JARs etc. do NOT prevent one form of structural failure, that of adhesion failure at the interface. Current advisory circulars also do not address the issue.
This must be backed up by a plethora of tests at coupon, detail, element, subcomponent and component tests. If they designed using Hart-Smith's equations to calculate the load capacity of the adhesive and then designed the joint to achieve that load capacity then every adhesive joint would NEVER fail. Every coupon..... etc. test would break the metal, so you could reduce the number of tests by an order of magnitude, thus saving millions on certification costs. As well as that materials substitution requires a simple calculation to show equivalent joint strength. In the current method, a complete substantiation program may be necessary.If the same approach was used for repair design and that was combinded with reliable validation of bonding processes, then such repairs would never fail, thus reducing maintenance costs.
I know of one repair on a 777 TE flap that has been repeated by a repair station crew four times. You'd think that they would relaise that there is a problem.
The real root of the problem is that the FARs JARs etc. do NOT prevent one form of structural failure, that of adhesion failure at the interface. Current advisory circulars also do not address the issue.
blakemax
I understand a small amount of Methanol is released in use of 6040(r) is this of any significance if used as a bonding agent on alloys ?
Any information to get good bonding is a + .
tracker69
Look what you have started & you only wanted to glue 2 bits together
I understand a small amount of Methanol is released in use of 6040(r) is this of any significance if used as a bonding agent on alloys ?
Any information to get good bonding is a + .
tracker69
Look what you have started & you only wanted to glue 2 bits together
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Being a Bank Holiday, (what Bank isnt on Holidays most other days?) I have just found my glue pot from the rear of the woodshed, used for sticking wings and other bits on Mossies, did pretty well until they flew through the rain or some kraut shot em down, I wonder if this will stick Ali! I'll heat it up and report back!!
Peter R-B
Well the old Glue pot nearly worked but the test piece came apart, so possibly best to forget the old glue pot!
Peter R-B
Well the old Glue pot nearly worked but the test piece came apart, so possibly best to forget the old glue pot!
Last edited by VfrpilotPB/2; 5th May 2009 at 11:00.
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Methanol and silane
G'day 500e. The method for using silane is to mix the solution in distilled water at 1% and to agitate the solution for one hour before use. This allows the silane to hydolise and that is when I believe that the methanol is released. Because of the low concentration used, the amount of methanol is about equivalent to a flea breaking wind, so it is not significant. To satisfy our OHS people (METHANOL!!!!!....AARGH, face mask respirator, evacuate the building type people) we actually had a registered agency measure the amount of methanol released and it was at such low levels it was almost undetectible.
Just a small aside. A colleague of mine approached the aforesaid OHS people asking what was the appropriate PPE for a weak solution of 1,1,1 trichloroethane and a white colouring agent. We were told to use respirators, goggles, gloves aprons, boots etc. It was whiteout correcting fluid.
Just a small aside. A colleague of mine approached the aforesaid OHS people asking what was the appropriate PPE for a weak solution of 1,1,1 trichloroethane and a white colouring agent. We were told to use respirators, goggles, gloves aprons, boots etc. It was whiteout correcting fluid.
Avoid imitations
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I have a couple of engines using methanol as fuel. How would they allow for the fuel to evaporate?
Never ran cars on Methanol but did run blown motor cycles and we always used to drain the fuel and run on petrol for a few seconds at end of day.
One of the drawbacks of methanol as a fuel is its corrosive to some metals, including aluminium. Methanol, although only a weak acid, attacks the oxide coating that normally protects the aluminium from corrosion:
blakemax love the remark regarding correcting fluid.
One of the drawbacks of methanol as a fuel is its corrosive to some metals, including aluminium. Methanol, although only a weak acid, attacks the oxide coating that normally protects the aluminium from corrosion:
blakemax love the remark regarding correcting fluid.
Last edited by 500e; 4th May 2009 at 20:45.
