Kynes,
Centrifugal force is a "convenience" used for quantitative discussion (more notably in Lagrangian Mechanics), but if you were to analyze the forces on a rotating body, what you are confusing as "centrifugal" is actually inertia.
Centrifugal would require a Newtonian force that exerts itself in a radial direction from the origin. When you let go of the ball on string, or a turbine fin has an instantaneously ubiquitous fracture at its base, what direction does the projectile go? OUTWARD?
No...
It goes in a direction tangential to the radial arc traced (i.e. the "theta hat" direction). It may appear outward, but it is not.
Take a look at the attached PDF from John Taylor's text-book discussing the "fictious" inertial forces and when they are "applied".
It's funny, I think back to when I was told these things, and I had the same sort of reaction as you. It took me a while (and lots of scribbling) to finally come to grips with the subject and accept it for what it is.
As for your powdered aluminum. An engine block is made from CAST aluminum, which is different from Aluminum alloys produced for general fabrication. Just like cast Steel is different from Structural Steel. Different crystal structures implies different reaction rates.
If you've ever tried welding any of these materials, you'd know exactly what I'm talking about.
So trying to use an example of how cast aluminum oxidizes versus aluminum plates or extrusions is not an apples to apples comparison.
BTW did you see the reply from the expert on that aluminum link of yours?
Materials want to achieve a lower energy state,(this is where Enthalpy comes in --Heck) in the case of Aluminum and steel they are more stable with an ionic bond between the metal and oxygen. This is basically the process of burning (i.e. add heat + O2, and you get an activated complex seeking the lowest energy state, being the Oxide); corrosion of the metals is the same process at a much slower speed. To compare Aluminum to Steel. Aluminum is more reactive than Steel, this is why it costs so much more to extract it from its ore.
However, aluminum is corrosion resistant because when it corrodes the surface of the plate is covered by the product of the corrosion. The product of this corrosion is Aluminum Oxide; this is a ceramic and is about the 3rd hardest substance known. The thin coating protects the aluminum under the surface and stops further corrosion. Steel on the other hand when it corrodes the Iron Ferrite peels straight off and exposes the underlying material this is why steel rusts so fast. Aluminum and Iron will burn as will any other metal, if it has a sufficiently sized particle. For both metals it is a very small size. A single plate will simply react on the outer layers however the outer skin will by covered in ash from the combustion and protect the inner plate.
Here's another useful link for identifying what type of alloy your engine block is made from before you go blast it with your pew-pew projectile-launching cylinder.
http://www.substech.com/dokuwiki/doku.php?id=cast_aluminum_alloys
The point is, you are not going to start any fires from blasting aluminum with projectiles or smashing a bat against a wall, either, unless one is dealing with a sufficient mass of free particles.
Go ahead and try smashing your noggin with an aluminum frying pan, and see if the pan turns to dust before catching on fire.
You can wear your fedora, too. For added excitement, try sprinkling some Iron (II) Oxide and Sulfur on top!
Hot time in the old town toniiiiiiiiight
Finally, my reference to the strength of aluminum going up under compression was not a reference to shooting it (I can see how you may have confused that). It was a reference to how a plane can punch through walls. Impact will compress the structure and components, increasing local strength (force vector dependent, of course).
This paradoxically allows for more penetration, albeit I am talking about tiny changes (probably approaching negligible, especially in the Flt. 77 case). However, it does not support the idea of increased weakness or fragility, which is a point some may try to make.
But heyyyy...I could be wrong, right?
teh fux?
i am aware centrifugal force is not a property of matter, and that it is a property of inertia, thats pure semantics.
objects in rotation, when released from their restraint move in a direction which is in fact the direction they would have been going if unrestrained.
if you wish to pretend that centrifugal force is imaginary, then you must also assign that same fictitious nature to inertia.
aluminium doesnt come in a forged variety, nor does it come in a super strong version that makes it suitable for use as armour, crush bearings, or in fact, any variety that will withstand forces that would heat it (low melt point), abrade it (low abrasion resistance) compress it (low hardness and low tensile strength) flex it (low malleability) or shock it (it is both weak and brittle when compared to steel or even copper). take a piece of aluminium stock and beat it with a hammer on an anvil, and in short order youll have tiny broken pieces ( i have done this)
as a solid chunk of stuff, aluminium doesnt burn readily, but if you shave it on a lathe, grind it with a file, or powder it with a grinding wheel, you can light it on fire easily (add a little iron oxide powder and you have a party!)
why doesnt your aluminium frying pan catch fire on the stove? because it transfers the heat throughout it's mass rapidly, making ignition difficult. as a powder it burns like a motherfucker.
alloying aluminium with other metals doesnt magically transform it into "adamantium" suitable for making wolverine style blades, it is still a weak brittle metal that spalls when applied with friction and pressure (thats why aluminium engine blocks have steel sleeves for the pistons), and while aluminium is highly resistant to natural oxidation thanks to it's patina of aluminium oxide which stops further oxidation, even a weak solution of any caustic material will pit it out rapidly (like when you put your aluminium pans in the dishwasher) in a stronger solution, it dissolves fast.
US Army tests on the Bradley Fighting Vehicle clearly demonstrated that when hit with a high velocity round (even non-incendiary rounds), aluminium armour can, and does powder then ignite. with a secondary fuel source it burns like a chanukah candle.
BLOCK aluminium "increases strength" when under pressure, but airplanes arent solid blocks of aluminium, they have "crumple zones" that allow it to collapse rather than resiting impact forces.
"stressed aluminium" has been used for a long time in making aircraft skins and fuselage structures, because it is LIGHT, not because it is particularly strong. "stressing" it allows you to make the shit even thinner without sacrificing much strength, but no matter how you slice it, aluminium is WEAK AND BRITTLE (not many aluminium knives, axes, wrenches, crowbars, hammers, or saws out there) it has shit strength. even titanium doesnt work well as a wrench or hammer because it is brittle.
if aluminium and it's alloys had the strength and versatility you ascribe to it, then my entire tool box would be full of shit made from this Wonder Metal Of The Millennium, but it aint.
