bonding 2 pieces of ali?

[tracker69]

Hi everyone

I’m looking for a ultra strong glue for bonding 2 pieces of aluminium approx 32` thick together. There are glues on the market for bonding in the rotary maintenance, does anyone know of any names etc? MUST BE ROCK HARD

[bluesafari]

What 'Ali' do you mean? If for aircraft use your maintence and structural repair manual will advise on authorised adhesives for particular applications

Unless it is not for aircraft use?

[tracker69]

its aircraft aluminium and is not for aircraft use.

[Chopper Doc]

Go to Halfords and buy yourself some araldite.

[tracker69]

areldite is rubbish,,,,,,

[Miles Gustaph]

araldite holds the wings of the Sukhoi 27 on... gee I wonder if anyone has told the Sukhoi Design Bureau...

[PPRuNe Towers]

This stuff has a very good reputation. I've used other products from them over the years and was impressed.

System Three: Products: SilverTip MetlWeld (http://www.systemthree.com/p_st_metlweld.asp)

JB Weld might be easier to source where you are though - sets hard enough to mill and thread tap.

Rob

[500e]

If you use Araldite clean with a degreaser then abrade with emery loaded with Araldite then if possible vacuum the joint during cure ( use the 24 hour not the fast cure Aroldite) have used this method for numerous projects on boats works well, carry out all operations as quickly as possible, also use minimum amount of glue.

[widgeon]

32' , is that 32 feet thick !! ( shades of Spinal tap here ) :)

[blakmax]

Dear me. The level of knowledge about adhesive bonding within the rotorheads community is really low. I suggest that you try reading DOT/FAA/AR – TN06/07, Apr 2007 BEST PRACTICE IN ADHESIVE BONDED STRUCTURES AND REPAIRS. You can get this document by emailing the FAA Tech Center. If you want a soft copy send me a private message.

Firstly, the selection of the adhesive is almost a trivial aspect of the technology. Most adhesive bonds do not fail through the adhesive, they fail through the interface between the adhesive and the metal. That form of failure is driven by the surface preparation prior to bonding. Can I assure you that if you "clean with a degreaser then abraid (abrade?) with emery" you will have a weak bond. Here is why:

Adhesive bonding depends on the development of chemical bonds between the adhesive and the metal. (It has very little to do with surface roughness.) To achive a good bond, the surface must be clean (so that the chemical reactions can occur), but it also must be chemically active, which is why the surface must be etched or abraded. If you do clean with a degreaser then abrade with emery you will get what appears initially to be a good bond. However, the interface between the adhesive and the metal will be susceptible to degradation over time and eventually the bond will fail. The mechanism is that the aluminium oxides formed immediately after abrasion will have an affinity for water and will form a hydrated oxide (bohemite). The chemical bonds formed initially dissociate so that the hydrated oxide can be formed, and this leads to disbonding. Hence it is essential that you treat the surface to produce chemical bonds that are resistant to hydration. Be careful though. There are many adhesive bond primers out there which are virtually useless. I suggest that you contact me or visit my web site Adhesion Associates (http://www.adhesionassociates.com)
If you follow this advice, then virtually any adhesive you select should provide a strong, durable bond. If you don't follow the advice, then it will not make any difference which adhesive you use. The only difference will be the colour of the disbond. Obviously, the amount of effort you wish to expend depends on the importance of the bond to structural integrity and the consequences of failure. If the joint is required to provide ongoing strength in a structure that is critical, then you must do everything you can to assure integrity of the bond. If the bond is nothing more than cosmetic and failure is inconsequential, then use a sealant. That will keep the material together probably better than an adhesive at least for a short period of time.


Regards
Blakmax

[outofwhack]

For what its worth - I glued the flywheel onto the crankshaft of a Morris 1100 car engine with 24hour Araldite Epoxy and it held forever.

The metal key had worn away causing the flywheel to freewheel and glue was a quick fix designed to get us home and it lasted till the normal demise of the car.

OOW

[blakmax]

Crikey OOW! My experiences with a Morris 1100 meant that your bond had to last the life of the vehicle.... about six months! :E
Seriously, a different application. You weren't really relying on the bond, you were relying on the bulk properties of the adhesive material, and that is a different requirement to transferring load through an interface. The consequences of failure would also have been less stringent than for a structural bond on an aircraft. But then, a broken down 1100 near Walgett at midnight can be pretty risky too!:uhoh:

Blakmax

[unstable load]

its aircraft aluminium and is not for aircraft use.

So, if you can get aircraft ally I assume you can get the adhesive too.
Depending on what you want to achieve,
HYSOL
Metalset
Magnabond
Proseal/Flame master tank sealant
Araldite
Cyanoacrylate
The list goes on.

[cockney steve]

SIKAFLEX....it's an isocyanate-curing polyurethane, iirc.
use to stick alloy car panels together and alloy to steel also to fit bonded -in glass.
Yhe stuff is rubbery when set and you can get high and low -modulus types. As with Epoxy (or soldering/brazing ) a relatively thin film is stronger. metal sheet will tear before the bond breaks.

Prep and priming are the key to a successful long-term bond.

[heli-cal]

Araldite and Metalset have always been excellent performers, working without failure when applied to correctly prepared materials, during my time using them in workshops.

When asked it they were good, I'd reply that they were so good, they'd stick air to water! http://i666.photobucket.com/albums/vv29/helixpteron/happy0009.gif

[fling-wing_1]

Metalset seems to work well but the Hysol products win for my money. Many manufacturers seem to agree and you can get them in the small squeeze tubes. McMasters has good prices. Check on the RC forums :ok:

[Gaseous]

I had a similar problem a while ago, Finally achieved a durable (so far) bond using a dental silane as a pre-treatment before epoxy. Dental silanes are hugely expensive though. I wonder if Max or anyone knows of an industrial version at a more reasonable cost?

[blakmax]

Hi Gaseous
You are absolutely correct. We have been using a silane (gamma glycidoxy propyl trimethoxy silane) since 1992 and we have reduced our repeat repair rate from 43% to :mad: near zero out of about 3500 repairs. Silane is a component in "Bojel" a sol-gel product developed by Boeing in kit form. The best results are achieved by sovent degreasing followed by a grit blast and IMMEDIATE application of the silane. Boeing recommend the use of a primer but our experience is that the silane IS a primer and is effective in corrosion prevention. If you can't find Bojel then try Dow Corning Z6040.
The difference between grit blast and hand abrade is significant. Grit blast where possible, but NOT in fuel tanks.
God it is good to find someone who knows that it is not just a process of selecting different "glues". :D
By the way, in the past I conducted a course in which I told the students that they needed to spell the name of the coupling agent gamma glycidoxy propyl trimethoxy silane before they could pass the course. I then set a question stating "Spell the name of the coupling agent gamma glycidoxy propyl trimethoxy silane". Would you believe that out of about fifty students who actually did attempt the question, only four got it right and it was written in front of them!!!

[ianp]

pop rivets, save you a load of hassle.

[Dark Star]

pop rivets, save you a load of hassle.


Maybe, but nothing like as strong, or durable, as a properly prepared and bonded adhesive joint. :ok:

[Gaseous]

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.

[cockney steve]

treating a trailing edge main rotor blade delamination to a quick slap of some stuff with "Bell Helicopter" written on the tube.

yep! like the motor-trade. "cleaning"the faces for a head-gasket seems to equate to scrape the worst off, scrub with emery-cloth, wipe with oily rag and it's good . They thought I was nuts using cellulose-thinner and white tissue to swab the faces AFTER a proper clean-off. when no more dirt came off, it was good to go. never had a failure.

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.

[blakmax]

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!

[blakmax]

Gaseous, I noted your comment:
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.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? :ugh::ugh::ugh:

I defy anyone to show me test results (other than just NDT) which show any shred of evidence that injection repairs achieve anything!!!

[Dark Star]

Lap-shear strength quoted in data sheets is a meaningless parameter.

So true, and hard to believe that people (who should know better) still quote it !

[blakmax]

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). :confused: 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. :ugh:

[500e]

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 :ok:

[VfrpilotPB/2]

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:hmm:


Well the old Glue pot nearly worked but the test piece came apart, so possibly best to forget the old glue pot!:ok:

[blakmax]

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.

[ShyTorque]

I have a couple of engines using methanol as fuel. How would they allow for the fuel to evaporate?

[500e]

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.

[HELOFAN]

Simple. TIG weld it.

Best Ali glue around.

HF

[K1W1phil]

Stick with "BlackMax" he actually knows what he is talking about!:ok:

[Bodgeit n leggit]

Hysol 93**. sticks S%&t to a tea towel, + aircraft.

[blakmax]

Thanks for the vote of confidence K1W1Phil. I owe you a Speights next time I'm in the shakey isles.

Blakmax