Any tips on bonding Aluminium to fiberglass (polyester). I have the option to use an anodised aluminium part if this helps.
I can lay up directly onto the Aluminium or use a structural adhesive. Polyurethane adhesive has been suggested as the way to go and does seem a lot cheaper than epoxy adhesive. Any recommendations?
Thanks
Well I don’t claim to be an expert on this but I did do quite a bit of reading and research regarding this topic a while back while working on a project involving bonding aluminum (7075) to some epoxy graphite tubes. What I would consider:
life span of your product: how long will it be in service?
what type of fiber: any potential for galvanic corrosion?
Environment: moisture, temp, UV, chemicals ect… This also plays into life span.
What type of anodizing? type II is primarily cosmetic, while type III has some definite advantages.
What I ended up doing was going with type III anodizing, not only to protect the aluminum, but also create a barrier against galvanic corrosion from the graphite fibers. I did however find out after while talking tech to my anodizing guy, that bonding to a type III surface with no dye is optimal. The dyes are usually organic based and penetrate the pores of the surface possibly degrading the bond. Those parts are still in use and have not had a single failure. I should add that I used a high temp structural epoxy. Just as bonding anything thing else clean clean clean is the name of the game. Hope I helped.
For bonding with little surface prep, use a methacrylate glue. Can be used on many surfaces.
When using epoxy, an anodisation layer can be beneficial, I believe Boeing has some patents on that.
Replacing after 3-5 years would be OK. However I would need to have a way to test bond as failure.
Think we are OK here as I’ll be using polyester resin and s-glass in contact with Al. No carbon in contact with Al
Will be splashed with salt water once every 2 weeks but not submersed. Temp would just be normal outdoor temps say -10c to +30c but could be exposed to direct sunlight for 8 hrs.
Not sure. Its dyed a bright colour. I think its either type 2 or 3. I’ll investigate.
Guys I work with have built super yacht rig before and they used hard anodising to improve aluminium to composite bonding. The theory goes that the anodising has micro pores that the resin bonds into.
Read up on BAC 5555.
PAA (phosphoric acid anodizing)
Reliable bonds to aluminum are really hard to do.
Even the slightest ambient moisture will form oxides on the aluminum before you have a chance to apply your adhesive and any real load will cause the bonded oxide layer to separate from the base aluminum.
In other words; it is going to break.
Not, it might break. …
It is going to. It’s just a question of when.
This is the same logic that was expressed to me by my andoizer, the dye penetrates into theses pores and may possibly not be compatible with the adhesive. I have yet to have a failure with hard anodizing and no dyed color.
So, do you suggest me to adonize the aluminiun 7075 piece to get better bonding properties with epoxy resin?
*(Sorry, but I’m not speak english and some phrases don’t understand very well)
Don’t apologize, I’ll say that if given a choice I would have it type III anodized.
Maybe this will help you
Just checked: Boeing uses phosphoric acid anodising.
Type III is hardcoat anodizing (HCA) for high wear performance and electrical insulation, and phosphoric acid anodizing (PAA) is used for metal bonding (structural adhesive).
looks like someone read it