New 'foam' core material?

[Stumble]

Always on the lookout for new ideas or technology I recently ran across a new type of 'foam' that I am curios about for use in cored structures. Basically it is a aluminium foam, than can be cast into parts, used to fill voids (though I am unsure how), or bought in 8x4 sheets and used like plywood. I am just curious about what others may think about it.

www.alusion.com
http://www.alusion.com/download/Cyma...Nov%202009.pdf

[Ike]

I am aware of aluminum honeycomb. It is used extensively in aircraft and to some extent in large yachts to reduce weight while retaining strength. Interesting product. I have not seen this before.

Thats not so very new, and sometimes used for engine room insulation, but there are cheaper and better (this is a dirt catcher) materials.
Al honeycomb has no advantage in boatbuilding imho.

Regards
Richard

[Ilan Voyager]

Big problems of corrosion with aluminum honeycomb in marine use, too heavy also and gluing problems. Has been dropped years ago.

[Chris Ostlind]

Except that we are not talking about honeycomb with this product. This is a foamed aluminum material and for certain applications, it might be an interesting alternative.

And Richard.. how is that there would be dirt in an engine room? What the heck kind of ship are you guys running there, anyway? ;-)

Originally Posted by Chris Ostlind

Except that we are not talking about honeycomb with this product. This is a foamed aluminum material and for certain applications, it might be an interesting alternative.

And Richard.. how is that there would be dirt in an engine room? What the heck kind of ship are you guys running there, anyway? ;-)

Well I did talk about the foam. (and the honeycomb)

And I do not operate my customers boats, generally they do. Impressively, some of them (say 95%), do that in a dusty environment, to some extend.

Regards
Richard

[Ilan Voyager]

The alu foam will have the same corrosion and bonding problems that the honeycomb, with a potential fire hazard added.

Knowing how aluminum burns hotly while being in thin thickness shapes (try a mix of diesel fuel and aluminum powder...very hot, thermite is made on that basis) I wouldn't try to put in a engine room a material that could be eventually soaked with oil, gas or diesel and able to have such a highly thermic reaction. For me it's a deadly combination, unless I have rational proof of the contrary.

Apart the fire hazard, for sound deadening uses there are a lot of efficient and well proven ignifugated solutions.

[Stumble]

Ilan,

Did you read anything about this stuff or just start spouting off crap to make yourself feel better?

It's density varies, but can be less than the nominal density of balsa wood. Doesn't sound to heavy for core applications.

It is chemically exacally the same as aluminium plate or aluminium foil, which I am pretty sure have been well tested in Marine and aerospace applications for years. And while yes it can be used as part of a thermite reaction, the most common oxidizer is iron rust... Does that mean we can't use any steel on boats because they could ignite?



This is a pretty different material than aluminium honeycomb, it was tested for fire proofing, and rated in as a 1 in the ASTM E 84 Flame spread and a 5 on Smoke development. This is compared to Red cedar which is used as the base line of 100 in both catagories. The Uniform Builging Code in the US for instance requires materials to have ratings of:
· A flame spread rating of 25 or less
· A smoke density rating of 50 or less


Now I don't know anything about this stuff, and was just curious about its use to replace balsa or foam cores in boats, since it is chemically as inert as aluminium, the same weight, and possibly immune to the type of 'rot' seen in foam and balsa applications.

On another note... Apex hates all cores in boat construction.

[Ilan Voyager]

Aluminum is not chemically inert, any welder can tell you that. Corrosion and eventual electrolitic corrosion could be a problem as it was with alu honeycombs (the combination carbon fiber and alu honeycomb was not a good one...) The problem is not in the chemical composition; the problem resides on the ratio surface exposed to oxygen/total weight, thus the capacity of fast oxydizing. A powder has the biggest ratio, a plate has a very low ratio. A foam must be somewhere between.

Aluminium oxydizes very fast. It's a common material used in pyrotechnics as it burns very well ( only surpassed by its cousin magnesium) and produces a lot of heat (and light). Iron oxide powder is a good contender by its content of oxygen. The variety of thermite we used had a lot of aluminium powder as starter, along with iron oxide.

My concern, as a former naval engineer having worked on warships where fire hazard is a great concern, is the event of a fire in a room engine with alu foam "contaminated" by any hydrocarbure.

I feel no confidence in the use of such a material in this place, and there are several other materials able to do the job. I wouldn't take the slightless risk simply because of the potential.

Ok in a "dry use" like building, but sorry, not in the presence of hydrocarbures. After all in 2001, everybody has seen the effects of aluminum burning with jetfuel and a lot of oxygen in the Twin Towers. Ok, not directly transposable, but ask any military engineer about aluminum and fuels fires; just reach the good temperature and you'll see the results oh this synergy.

[Stumble]

Ilan,

I see what you are driving at...

But I am not sure that I see a great distinction between a fiberglass encapsulated aluminium foam, and say traditional foam or balsa cores, either of which can burn relatively quickly.

Secondly I doubt the amount of fuel that could penetrate into the core would be all that great. Certainly capillary action could carry it up a ways assuming a breach in the skin, but I wouldn't consider a cored bottom on any boat, of any material, so I don't see long submersion times being likely. Or at least in the even that they do occur the boat is having pretty bad problems anyway.

[Ilan Voyager]

None of these materials are suitable in a engine room. You have a lot of possibilty of contamination; diesel, gas, oils (engine oil, hydraulic fluid) and greases. You would be surprised to see how easily fuels and oils can go through and destroy polyester, we have seen that on GRP foam mine hunters.

A lot of european boats have cored bottoms without problems, even after 25 years at sea like the old Geronimo trimaran. The true problem is the traditionnal use of orthophtalic resins by most american shipyards. European shipyards use mainly isophtalic polyester resins, and chop gun is a tool forgotten since a long time except in low quality and cheap applications. It's impossible to get a waterproof GRP with orthophtalic resins, and less with a chop gun where a lot of air microbubbles remain.

[Fanie]

If you try to buy fine alluminum granuals you are under suspicion of making bombs, fine allu does burn. Thin Allu will corrode unless specially treated, and then any treated material will work.

Aparently the Germans started to use a corrugated profile instead of the honeycomb, aparently stronger and they save something like 25% on the plane's weight. Maybe the same can be done on boats.

Originally Posted by Stumble

On another note... Apex hates all cores in boat construction.

This last statement is not true. Actually I am planning to build a cored boat, but that will be a completely different animal to the common construction.

I´ll keep you informed.

To Ilan´s concerns,

I fully concur with the statement about the rather high risks of these (and similar) Al foams.

There is always some oily vapour in engine rooms which can penetrate the material.

Same concern as others I have with corrosion,
The honeycomb, used in the past, DID corrode. So, why should the foam be resistant? There is even a higher surface to weight ratio in the foam, giving a higher risk of corrosion.

Regards
Richard

[Chris Ostlind]

Ilan, really...

You complain about sandwich laminate alu foam core structures as enhancing fire potential and in the same breath you talk about engine rooms that are full of flammable materials such as hot engines, paint, grease, lubricants and the big one... fuel itself?

Come on, man, this rant is sounding like a mother who is screaming at her kids for playing with wooden swords when her kitchen is full of knives, forks, skewers and big hunks of glass objects for holding fluids.

This is not alu powder and somehow I suspect that you already know that and just want to make it guilt by association without really having any hard data to support your argument.

[ancient kayaker]

I don't see why Al should be a significant fire risk. It needs an oxidiser, so does a hydrocarbon fuel, they cannot interact with each other to sustain a fire, both need oxygen.

Al can be ignited but at very high temperatures. This is a problem in warships with Al superstructure such as HMS Sheffield which burned for days and finally sank following an Exocet hit during the Falklands War, but even an engine room fire is unlikely to reach such temperatures.

Not sure why Al powder is being discussed since it is not used for making foamed Aluminum. This product has gas bubbles introduced into the molten metal; the other constituent is a ceramic.

Nonetheless, with the bending and adhesion problems reported it seems unlikely that it will see much use in boat building outside of high-tech products. Might make an interesting material for masts and booms however.

EDIT: this is incorrect, Sheffield was an all steel ship, please refer to following posts for data