Jump to content

epoxy/aluminium construction ?

Guest micgrace

Recommended Posts

Guest micgrace

Hi, probably a question for Ian


Do you have any recomendations


or advice on bonding aluminium together with epoxy? i.e. CASA


viewpoint, material and practice acceptable.





Link to comment
Share on other sites

As a former RAAF 'Aerostructures' repairer with a bit of


background in bonded structures, be prepared to pay lots of money for


not only the exotic epoxies, but the infrastructure that goes with them;Freezers,Vac bag systems,Autoclaving systems,Cleansuits,Etch chemicals.That's not to say it's impossible, but a purely bonded Primary structure means you have to be real sure that it all sticks together.The main problem with bonding aluminum (or any metal)


is that you need to create some form of textured surface for the


adhesive to hang onto, many think that bonding is like that trick where


you can hold two polished surfaces together with a drop of water.Unfortunately this has no shear load ability, and this is the most typical load requirement in aerostructures.Many of the repairs I do, stem from the use of slightly acidic (or alcalinic) epoxies to help etch at the bond site.This


can work for a while, but eventually heat and flexing movement will


allow moisture to enter the join and combine with acid residues to


attack at the bond surface.In a recent example a Cessna 182 of about the 70's era (that's a later one!!) turned up with bulging at the ribs on the leading edges.The early (50's & 60's)


Cessnas' had rivetted ribs in the leading edges, the later ones are


bonded for a quicker and better finish, but this one had de-bonded most


of the ribs and started to corrode the leading edge skins.Remember, I'm talking here about primary structures, you really need to say where you want to go bonding stuff....There are lots of discussions about this sort of thing on a really good homebuilders site in the US;goto http://www.homebuiltairplanes.com/forums/Arthur.



Link to comment
Share on other sites

Guest micgrace

Thanks Arthur,


I was not going to use the bonding purely on


it's on, or as a substitute, and not on primary structure, and then


only with rivet backup (mainly to eliminate squeaks i.e. for those that know, not the audible kind). This is for a 95.10, so some info on a suitable (uncertified) method is appreciated.





Link to comment
Share on other sites

Guest micgrace

Thanks again.


From the site you mentioned, this appears to be


the holy grail of aviation, a simple expoxy compound that reliably bond


aluminium without the extensive procedures you have used.


Apparently some of the Hysol products are used in homebuilts (namely 956)with useage of fasteners to prevent peel and to add thier own measure of strength.


I might do some experiments to see for myself what could be used.





Link to comment
Share on other sites

i have worked with HYSOL products for many years, namly on Boeing


aircraft, the 747 and 767. 956 was used to bond aluminium and


composites together as well as bonding alluminium to other metals., (other


hysol resins boeing approved are Hysol 956, 3130, K230 and 304, there


are otehrs but require temps of approx 3 or 400 deg to cure) the


alloy surface was lightly scuffed with scotchbrite to give the resin a


key surface, then lightly primed with a bonding primer, i cant remember


the name but it was a very pale yellow colour, and applied very thinly,


dipping a rag into the primer, then drying the rag onto a clean rag,


then using the almost dry rag to apply the primer..


heat was applied as well as vacumn, heat can be provided by heat lamps, (similar to automotive panel beaters use)


or heated blankets controlled by a computer or in an autoclave. in the


field as many of our repairs were, vacumn can be provided by a air


operated ventury, or vacumn cleaner, thermocouples placed on the bonded


area and connected to a multimeter to read the temperature, and


manually move the heat lamps as the temperature is reached at the bond




though most Hysol resins will also allow room temperature curing,


though this usually takes a few days at 21 deg C and vacumn can be


maintained for the time of a cure.. vacumn and heat are not essential


but preferred. vacumn can be replaced by clamps and weights depending


on the job being bonded.



Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...