How good would Aluminum armor be?

[Tyneras]

If I make a breastplate out of aluminum, how much DR would it give? If you need numbers, assume a DR 6 medium plate breastplate, only made from aluminum (same thickness, it would obviously be lighter, 2.7g/cm^3 vs 7.8g/cm^3). I'm rolling with the idea of early aluminum refining from Fantasy Tech and seeing where it takes me.

[Crakkerjakk]

Probably DR 2 if you're keeping volume the same. Most aluminum alloys are way too soft for armor.

[Anthony]

This is almost a FAQ, though I doubt it has a good answer, by the time aluminum could be made in quantities suitable for plate no-one wore plate. It's probably 1/3 weight, DR 2-3 (possibly DR 2, 3 vs crushing), and TL 6.

[DanHoward]

Pound for pound it should be a lot worse than steel. Otherwise aluminium would have been used for armour today.

[Fred Brackin]

Originally Posted by DanHoward

Pound for pound it should be a lot worse than steel. Otherwise aluminium would have been used for armour today.

Technically, it has been used for vehicular armor (Vietnam-era M-113 if nothing else).

Only in light roles, moslty for anti-fragment level protection and due to aluminum's predilection for catching fire it's no longer used for such purposes.

[mhd]

Isn't aluminium oxide a pretty common ceramic for body armor inserts?

There seem to be a few aluminium alloys that are DoD approved for vehicular armor. Don't ask me for which vehicles, though… (Edit: Seems at least some Bradley CFVs use 'em)

[mlangsdorf]

We do use aluminum armor today: the M113 and the M2 Bradley AFVs both use aluminum, specifically because it gives the same protection as steel at a slightly lighter weight. I'm sure other light AFVs do the same.

I can't find any specific cites in a quick web search, but I expect aluminum has a bulk issue that makes it impractical for personal body armor: at the thicknesses you can actually move in while wearing it, it doesn't provide enough protection compared to the same volume of steel, though it is lighter. So pound for pound, it's roughly equivalent, but per cubic inch it's much, much worse. If you're armoring a light tracked vehicle or a thin skinned warship, that's not a big deal, since you can just use thicker slabs. If you're armoring a person or a heavy tank, you run into size constraints. Aluminum also looks to be at least twice as expensive (per pound) as armor grade steel.

So for body armor (or other volume limited applications), I'd expect something like 40% of the weight of steel, about 1/2 the DR, and the same cost. If you can increase the thickness, 90% of the weight of steel, same DR, and twice the cost is reasonable.

Ninja'd by Fred!

[Anthony]

Originally Posted by DanHoward

Pound for pound it should be a lot worse than steel. Otherwise aluminium would have been used for armour today.

It has been used for armor, but it underperforms high strength alloys that are available at the same basic TL as aluminum, at least against bullets (crush protection is probably better). That doesn't mean it isn't competitive with TL 3-4 wrought iron. The big problem with aluminum armor is that aluminum is fairly soft and bulky.

[David Johnston2]

Originally Posted by Anthony

It has been used for armor, but it underperforms high strength alloys that are available at the same basic TL as aluminum, at least against bullets (crush protection is probably better). That doesn't mean it isn't competitive with TL 3-4 wrought iron. The big problem with aluminum armor is that aluminum is fairly soft and bulky.

"Bends easily" is actually a pretty good thing when you're up against bullets and tank shells. Not so good against bludgeoning weapons.

[Dammann]

If you have the ability to anodize, I could see a pretty effective laminate made from aluminum. Aluminum oxide is pretty hard stuff, although raw aluminum is very soft.

I suppose the ideal would be the ability to do type III anodizing. That gives you the best hardness and thickness for durability, but requires temperature control and current control. It's probably beyond the means of any sub-kevlar technology base. Heck, steel is probably a more practical even-lower-tech alternative.