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Roberto Amato 20th October 2003 11:11 PM

Aluminum Glue
 
I need to hold together some aluminium parts without using nor screws nor slots. In other words the bonding has not to be visible. I heard that in avionics and aerospace are used some kind of glues that are capable to bond together aluminium in such a strong way that it seems to be welded. Anyone have ever had experience with this kind of stuff? And even more important, any idea where is possible to buy it in small quantities?

ciao,
Roberto Amato

Christer 20th October 2003 11:21 PM

In fact, I do have experience with such a glue. I've used it to
repair an aluminium easel that broke during a rainstorm in
France. I have no idea where or if you can buy it though. I got
it from my father who used to work for Saab Aerospace who
use it to glue aircrafts. My father tends to use it for almost
everything that need to be glued and it is very strong indeed.
It is not very healthy to work with, though, but most strong
glues aren't, of course.

Sch3mat1c 20th October 2003 11:24 PM

Just use epoxy.

As with any glue the metal has to be immaculately clean for good bonding, like that it should work pretty well; but you can go it one better with aluminum: wet some sandpaper (80~250 grit) with the mixed epoxy (you wouldn't want to use 60sec. stuff here! ;) ) and sand both mating surfaces until they've been evenly abraded. Make sure the metal surface never gets exposed to the air, keep a film of epoxy on it. Clamp the surfaces together until the epoxy sets. Don't worry about grit in the joint, think of it as filler - and they make plenty of filled epoxies. :)

Tim

Roberto Amato 20th October 2003 11:51 PM

Quote:

Originally posted by Sch3mat1c
Just use epoxy.

As with any glue the metal has to be immaculately clean for good bonding, like that it should work pretty well; but you can go it one better with aluminum: wet some sandpaper (80~250 grit) with the mixed epoxy (you wouldn't want to use 60sec. stuff here! ;) ) and sand both mating surfaces until they've been evenly abraded. Make sure the metal surface never gets exposed to the air, keep a film of epoxy on it. Clamp the surfaces together until the epoxy sets. Don't worry about grit in the joint, think of it as filler - and they make plenty of filled epoxies. :)

Tim

I'm afraid that epoxy, if gets a sharp whack, just looses its grip... as does generic cyanoacrilate (I tried it). The bonding is between a rectangular extruded aluminium bars and two aluminium plates that closes both ends. The bar edge is 4mm thick. Besides I have to do many of those and I would prefer some faster way...
Thanks for the idea, anyway, it's interesting by itself.

Clearly, the glue Christer mentioned is the one I'm looking for,
fast and strong... no brand name?

ciao,
Roberto Amato

Christer 20th October 2003 11:54 PM

Quote:

Originally posted by Roberto Amato


Clearly, the glue Christer mentioned is the one I'm looking for,
fast and strong... no brand name?

No idea at all, I am afraid. I only know it is some nasty green
stuff. Maybe Peter Daniel knows, he works or has worked in
the aircraft industry if I don't misremember.

Edit: I should perhaps add that this particular glue is AFAIK
primarily for gluing composites but it seems to work well on
aluminium and pretty much anything else too.

Peter Daniel 21st October 2003 12:05 AM

Unfortunately I never glued aircraft parts. I only used some structural adhesive (generally 2 parts epoxy) and cyanoacrilate in my projects. The last one is pretty convenient, but indeed brakes when given a sharp whack.

You might try some construction adhesive, which is more flexible. Most of them adhere to metals and they are pretty strong.

Squalish 21st October 2003 12:06 AM

Isn't epoxy a generic term describing many glues of a certain class of chemical composition?

JB Weld is one of the most popular products that seems to fit your application. There are thousands of glues out there that claim to bond strong as steel and better.

Peter Daniel 21st October 2003 12:08 AM

I tried JB weld, but the bond was nothing comparable to steel;) Of course it largely depends on the way the parts behave.

purplepeople 21st October 2003 12:15 AM

It may be one of the 400 series cyanoacrylates from Loctite. I've used both 454 and 411 and they are great adhesives. Fast and strong and waaaayyyy better than Krazy Glue. These are serious industrial strength adhesives that can work in as little as 10 secs. But, they require next to zero gap between the pieces.

And don't count out the epoxies. These are available in strengths of 5minute, 1hour, 1ton, 2ton, 5ton, etc. One of these has got to be strong enough. You might be able to get some small amounts from Devcon in a double syringe. Just depress the plunger and exactly the right amounts spill out onto your mixing surface. Advice: it is very easy to inject too much and you end up with waste of fairly expensive liquid.

Aluminum is self-anodizing and that may be your problem. If you just bond the two parts together without exposing the raw aluminum then the joint will be quite weak. If you sand or file the surfaces to get to the raw metal before using adhesive, you may have also rounded the surfaces creating a gap between the two pieces. That gap is death to most adhesives. That filler approach suggested by Tim should help to solve that problem.

:)ensen.

OliverD 21st October 2003 12:17 AM

The glue we use for composite components in our aircraft is a mixture of L286 resin (with hardener, of course), cotton flakes and aerosil (don't know the english term). One big advantage of this mixture is that it works as filler and glue at the same time. It works also good on metals, but it depends on what you want to do. How big is the area the glue will be distributed on? What forces do you expect?

There are various 2-component glues from a company called "Araldit". Their products are also very good for metals. The glue we use (don't remember the product name) never gets completely hard which is a big advantage in some cases (it won't break).


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