Embedding aluminum structure in urethane foam -- issues?

[Foreigner]

Hey everybody

I have a non-boat question regarding a self-designed project I am doing at work. As I look for resources on this project, boat-builders seem to have the most experience with this sort of thing. I have never built boats, but with the cool stuff I am doing in R&D right now and seeing some of the stuff on this site, I'd love to jump in!

I am working with 2-part urethane pour foam (currently supplied by SPI and US Composites) that serves as the main structure. I need to have attachment points and more rigidity, due to its dimensions - 2"x18"x60." My thought at this point is to embed a thin aluminum structure with threaded studs for attachment. I have done several prototypes that are definitely in spec, but am concerned about the long term viability of it.

Does anyone have experience with this sort of thing? Could you share photos (or tell me where to find them online) of aluminum-embedded foam?

Another issue is the possibility of using the aluminum as a conductor for electrics (12vdc). I have done a two-part frame to carry positive on one and negative on the other. Anybody see a problem with this?

Thanks!
Nate

The industry uses PU foam injection between Aluminium panels since ages for cold room segments, with no trouble.

"Foster" is doing it in large scale.

Dunno if that info was helpful, but it is the only application I am aware of without thinking.

Regards
Richard

[mydauphin]

Aluminum is fine for conducting electricity but be careful if it gets wet and shorts together and you form a make shift battery that eats your frame. On aluminum frame in foam also be careful of corrosion if foam gets wets and stays in contact with aluminum. You may want to treat or paint aluminum.

[PAR]

I use structural foam panels in a few of my designs and they work well, though poured foam needs exceptionally controlled conditions to work well and uniformly in this role. It's easier to laminate sheet foam with other materials (plywood, sheet aluminum, sheet steel, etc.) then do a pour type of build method. There are several reasons for this. Naturally, the obvious one is the rapid expansion issue. This can be quite surprising and tremendous loads can be imposed on a mold. Meaning the mold has to be one tough piece of equipment and will probably need temperature control internally as well.

The ability of the polyurethane to stick with a uniform peel strength, is key to a serviceable foam panel. This is only possible with temperature and humidity within a fairly fine window. This is true of a panel or a foam filled area, designed to be load bearing.

I've used extruded aluminum I beams inside foam panels with C channel extrusions on the edges so the can be mechanically attached to each other. I've not used pour in foam for these panels, because of the points noted, but have made up sheet foam panels with this construction. They are light and strong, but not inexpensive and not necessary easy to do, unless you can assembly line a bunch of them at once.

As far as aluminum as you conductor, don't do it, it will not last long. Aluminum oxidizes naturally and this has to be accounted for annually. In other words, to make it work reliably, you'd have to torque up the contacts (each and every one) each year to insure oxidation hasn't degraded the connections.

Originally Posted by PAR

There are several reasons for this. Naturally, the obvious one is the rapid expansion issue. This can be quite surprising and tremendous loads can be imposed on a mold. Meaning the mold has to be one tough piece of equipment and will probably need temperature control internally as well.

When I remember well (from 1982), the Foster factory in Kings Lynn UK, had a jig which withstood a pressure of about 100 tonnes. This jig was used to "shoot" 4 or 6 panels of about 1,25 x 2,2 meter at the same go. For me it was quite impressive to see this massive jig for such a job. I mean, two wobbly sheets of nothing and some foam, what was that?

[Ad Hoc]

The main issue i would be concerned with is the foam hygroscopic? If so don't use it. You'll get poultice corrosion. Anything that is a "wick-like" material laid against ally will cause poultice corrosion.

Which is why panels that are laminated work well. They have an adhesive which acts a as a sealant as a water barrier.

[PAR]

I have speced and used epoxy John, which solves the few issues nicely.

[Ad Hoc]

Originally Posted by PAR

I have speced and used epoxy John, which solves the few issues nicely.

Got to wake up pretty early in the morning to catch you out...!!!

Nate.

Are you building a Windmill? Are these going to be Offshore Windmills.



What company?

Are you guys hiring? Would you need a Field Engineer?


Here is a Freebee Consultation answer to you question

aluminum as a conductor for electrics.

the Answer is NO,NO,Hell NO!

You will get corrosion and it is not a good conductor to begin with. Just use tinned Multi Strand shielded Copper

Capt Walt

WickeGoodOUtdoors@Maine.rr.com


( If you can think it? I Can sink it!) Expert in Destructive Field Testing.

[Foreigner]

Originally Posted by Ad Hoc

The main issue i would be concerned with is the foam hygroscopic? If so don't use it. You'll get poultice corrosion. Anything that is a "wick-like" material laid against ally will cause poultice corrosion.

Which is why panels that are laminated work well. They have an adhesive which acts a as a sealant as a water barrier.

The entire panel will be coated with fiberglass with the aluminum encapsulated. The foam is a closed-cell and the only way it will see that much water is if someone is very stupid.

Originally Posted by WickedGood

Nate.
Are you building a Windmill? Are these going to be Offshore Windmills.
What company?
Are you guys hiring? Would you need a Field Engineer?
Here is a Freebee Consultation answer to you question
aluminum as a conductor for electrics.
the Answer is NO,NO,Hell NO!
You will get corrosion and it is not a good conductor to begin with. Just use tinned Multi Strand shielded Copper
Capt Walt
WickeGoodOUtdoors@Maine.rr.com

( If you can think it? I Can sink it!) Expert in Destructive Field Testing.

No, no windmill, nothing offshore. Not allowed to divulge company or any other project details. Sorry.

Aluminum as a conductor is not a problem. It is already heavily integrated into our current products (and probably your house/power grid). We have had products in the field for over 15 years with virtually no oxidation/corrosion problems, but I have an electrical engineer for those issues.

The purpose of using aluminum in this case (as in current products) is the ability to use it as a structure+electrical.

[PAR]

Aluminum as a conductor is not a problem. It is already heavily integrated into our current products (and probably your house/power grid). We have had products in the field for over 15 years with virtually no oxidation/corrosion problems, but I have an electrical engineer for those issues.

You better re-evaluate your in field assessments and preform a search for aluminum wiring. This set of issues (expansion, coating, corrosion, contact lose, etc.) have all been carefully addressed.

AH?


If he is using n his house. I bet that the house is nowhere near the Ocean.
I get salt spray thru the windowns of my house on foggy days.

The Alum wiring may work in house seen in picture "A" but not in picture "B"

[Ad Hoc]

Originally Posted by WickedGood

I bet that the house is nowhere near the Ocean.

And i bet he doesn't live in a vacuum too...

[CDK]

There are some confusing and contradicting opinions here about the use of aluminum as an electric conductor.

Let me assure you that the whole world uses it in the power grid.
My house has copper wiring, but the main fuses are connected with Al cables coming from the high voltage transformer half a mile away. The transformer itself may use Cu or Al, depending on who built it. The 40 kV supply cable with a length of approx. 8 miles surely is Al, and so is the whole 200 kV grid.

Connecting such Al cables is done with giant crimp terminals, done on location with a battery operated tool with a ratchet construction to obtain the many tons of pressure required. Both cable and terminal deform in this process so there are no capillaries left and no protection is necessary.

[Foreigner]

Originally Posted by CDK

Let me assure you that the whole world uses it in the power grid.
My house has copper wiring, but the main fuses are connected with Al cables coming from the high voltage transformer half a mile away. The transformer itself may use Cu or Al, depending on who built it. The 40 kV supply cable with a length of approx. 8 miles surely is Al, and so is the whole 200 kV grid.

What ^^ he said.

I am not here to debate the uses of Al as a conductor. As stated, we have products in most of the lower 48, many of which are in coastal areas. No problem.