Is air a "material"?

>>8165856
Air by definition is a material, otherwise it would be a vacuum.

>>8165867
This.

>>8165867

But does it count as a material in a design where it wasn't added, and it just happens to be there, because the design has empty spaces in it?

>>8165873
It is either a material, or a vacuum.

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>>8165872
>There are 2 posters in this thread.

You can't fucking "This." your own post you fucking faggot.

I fucking caught you. Fuck off.

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>>8165856
Air is made of matter, so if it's used to make something, it's a material. However, in this case, the air is incidental to the structure. The functional part of those gaps is the gaps themselves. Filling them with air, argon, foam, or vacuum would not matter for the armor's function. Similar to a truss or castellated beam, the gaps in the structure are what matter, not the air that happens to fill them.

This is all semantics, of course.

>>8165867
>>8165872
>>8165875
>>8165876
What're you going on about?

>>8165886

thank you, that's basically what I was trying to get across on the other thread but you wrote it in a much better way than I did.

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>>8165888
<- See picture.

>>8165876
Which means OP posted three times, as I am >>8165867 and this is my second post in this thread.

>>8165873
think of it this way. if you modelled something in CAD or some software like MCNP, if you left a volume blank with no material, would it interpret it as air or a vacuum (assuming you're not given an error)

>>8165886
Air is used because otherwise you would have to seal the chambers, adding weight and manufacturing costs as well as the need to periodically refil.

>>8165907
Fuck no, air would be pointless, as air is highly compressible (you might as well fill it with water, something that isn't highly compressible).

>>8165910

I screencapped the thread at the wrong time so my image was meaningless,

but i still post the question:

If any of you /sci/ guys know the difference/similarities between spaced armor and composite armor, do air gaps count as "composite armor"?

>>8165916
>Fuck no, air would be pointless, as air is highly compressible (you might as well fill it with water, something that isn't highly compressible).
^ To reiterate.

>>8165907
The 'air gaps' were intentionally added and serve a purpose (rapidly changing densities and elasticity), arguing that they are not part of the composite armor's structure is silly.

>>8165916
Air is a component in a material. A material can have many components, including air.

Holy shit people.

>>8165906
Typically vacuum. Air is considered for physics calculations like wind loads, but it's typically not used in the actual design files. It's not going to list air on the bill of materials.

>>8165908
>Air is used
>is used
Nice weasel with the passive voice there. No one specifically puts air there. It just happens to be there since it's not specifically kept out. It is irrelevant to the function of the armor. Would you say that air "is used" to fill the gaps in a truss bridge?

>>8165936
>A material can have many components, including air.
True, but that doesn't mean that every structure that doesn't specifically exclude air has air as a component. Air is a material component of hot air balloons. Replacing the air with vacuum would prevent the balloon from functioning. Air is not a material component of spaced armor. Removing the air would not alter the function of the armor.

>>8165910
>>8165925
The fact that air is highly compressible is a factor in its fuction. The copper 'spike' of HEAT warheads are extremely brittle and do not like layers of different material, passing through an 'air gap' is a shock for the 'spike'.

>>8165906
>>8165937
The exception would be balloon structures where air pressure is used to inflate things, and in those cases it's net pressure that matters, not the absolute amount of air there.

>>8165886
>filling it with vacuum
Once I took 7 vacuum and placed in a box with a maximum Volume of 10 Vacuum and filled the rest with Diamonds and in the next day I had 8 Vacuum but still the amount of Diamonds. Therefor: diamond are the hardest Metall

>>8165943
Based upon what scientific principle?

>>8165943
>extremely brittle
It's superplastic, not brittle. Spaces with different density disrupt its flow, not make it crack. The density difference between air and vacuum is negligible in this case.

>>8165937
>No one specifically puts air there. It just happens to be there since

I like how you specifically ignored that I addressed why air is used.

>>8165956
But the density difference between air and say, rubber, is significant.

>>8165958
Fine, put rubber in the spaces.

>>8165958
Last I checked, rubber wasn't latent to our atmosphere.

>>8165961
or better yet use both rubber and air

>>8165963
And?

>>8165937
>It's not going to list air on the bill of materials
but it is listed as a material choice as an input into the design

It's not really air itself, it's just open space. You don't say that, for example, a skyscraper is mostly made up of air.

>>8165979
>a skyscraper is mostly made up of air
because by weight its not

>>8165957
>why air is used
There it is again. It's the gaps themselves that matter for the armor's function, not the air that happens to fill them since the gaps aren't sealed against it. If you put the tank in a vacuum chamber, the gaps wouldn't be filled with air any more, but the armor would work exactly the same. Because it's the gaps that matter, not the air that fills them. You know like a truss. A steel truss is not a composite structure even though it has gaps that are usually filled with air, because the air is not a component of the truss.

>>8165958
And? A steel/rubber sandwich is a composite whether or not it's spaced. Rubber layers with air gaps would not be a composite unless the air plays some structural role in the assembly.

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>>8165856
Yes, Air has certain properties just like everything else. If you're consciously using these properties I'd say it classifies as a material.

>>8165985
>>8165886
>>8165937

>A steel truss is not a composite structure even though it has gaps that are usually filled with air, because the air is not a component of the truss.
>Would you say that air "is used" to fill the gaps in a truss bridge?
>However, in this case, the air is incidental to the structure.

Air is incidental, but the fact that it's a gas is precisely why it works in the first place... It's not analogous to a truss because we aren't talking about trying to bear a load through the entire structure.

A shaped charge is formed by the pressure of an explosion. Setting off the shaped charge and allowing it to expand into an open space (filled with a gas) results in it being improperly formed or otherwise having dissipated its energy when it strikes the innermost armor plate. Changing the density of that gas will obviously change the resistance against that expansion and have some effect upon the effectiveness of the armor.

>>8165937
>>8165856
You (and many people in this thread) are quibbling over semantics. Air is *matter*. Whether it is "material" depends on the context and your preferred definition.

>typically vacuum
I don't agree with this. It's more like "no force calculations" to the cad/sim software. If it were vacuum there would be forces.

>>8166019
>why it works
But what "work" is the air itself doing? What is the functional difference between spaced armor filled with air, spaced armor filled with some other gas, and spaced armor filled with no gas (a vacuum)?

It is EXACTLY analogous to a truss, because as with spaced armor, what goes in the open spaces of the structure doesn't matter for the performance of the structure. That's literally an analogy right there.

>>8166047
>If it were vacuum there would be forces.
How so? Air on both sides of a wall = zero net forces. Vacuum on both sides of a wall = zero net forces.

>>8166047
>quibbling over semantics
That's specifically what OP's question concerns.

>Whether it is "material" depends on the context and your preferred definition.
How about the dictionary?
material noun (PHYSICAL THING)
› [C] a type of physical thing, such as wood, stone, or plastic, having qualities that allow it to be used to make other things:
a hard/soft material
The sculpture was made of various materials, including steel, copper wire, and rubber. - Cambridge

The air isn't serving a structural or other functional purpose in spaced armor. It just happens to be there since it wasn't specifically kept out. It is not "used to make" the armor, which would be unaffected by its absence.

Isn't air how insulation works? Seems to me it's very much a material.

>>8165987
>consciously using
>air is a material when being thought of, it is not a material otherwise

>>8166066
Air is a less effective insulator than vacuum. Open air spaces are poor insulators. Fibrous/foam insulation works by preventing air from moving around and taking heat with it, leaving its relatively low heat conduction (still higher than a vacuum). Air can be considered a material in such insulation (though it would work better in a vacuum without it), but spaced armor does not use air for insulation.

>>8166049

>But what "work" is the air itself doing?

Providing a space with less resistance for the penetrator to break apart and the explosive force behind it to dissipate.

>What is the functional difference between spaced armor filled with air, spaced armor filled with some other gas, and spaced armor filled with no gas (a vacuum)?

Obviously something moving through a gas is going to be effected by the density of that gas. This is why aircraft fly faster and more efficiently at 30000ft than they do at sea level.

Try using your brain.

>>8166072
>air is a material when being used in the design of something, it is not a material otherwise

>>8165985
>Rubber layers with air gaps would not be a composite unless the air plays some structural role in the assembly.

Considering the air plays a role in the structures function as armor, it is safe to say it is composite.

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>>8166084
>Providing a space
The space is provided by the metal/ceramic/whatever structure of the armor, not he air that happens to fill it. Compare and contrast to a truss and a hot air balloon respectively.

>Try using your brain.
The air is on the order of a ten thousandth of the density of the armor. Air being there or not makes less difference to the armor's effectiveness than a coat of paint. Do you think that an inch of air would make a difference to an aircraft ramming into a steel wall, as opposed to an inch of helium or an inch of uranium hexafluoride?

>>8165979
>It's not really air itself, it's just open space

To be more specific, it is a material of low density.

>>8166108
What function is that?

>>8166110
Do you really not understand that it is because air has such little density that it is used as a material in composite armor?

>>8165873
It is a material however in that application it's presence isn't part of the design. It would have water there or the vacuum of outer space and the function of the product would remain the same.

The engineering behind >>8165856 is 3 things. 1, is the use of all the extra surfaces in order to create more strength. 2, is to confuse any type of smart weapon so that it discharges its payload prematurely without reaching the inside of the tank. 3, it helps direct and absorb blast energy away from the inside of the tank.

>>8166112
Try reading the thread again.

>>8166120
>2, is to confuse any type of smart weapon so that it discharges its payload prematurely without reaching the inside of the tank

You were doing pretty good until you got to this point.

>>8166085
That isn't what material means. Whether or not you're using it is irrelevant.

>>8166116
>it is used
Passive voice again. Vacuum would work better than air in spaced armor, but not enough better to justify the hassle of maintaining it. The functional aspect of the spaces is the spaces themselves, not the air that's not worth the effort of keeping out.

>>8166122
I see that it's the gaps in spaced armor that matter, not the air. Gotcha.

>>8166127
See >>8166060

>>8166125
Some projectiles are designed to blow up the instant they reach a void. Everything from tank armor to bunkers have voids to help trigger the explosive payload before it reaches the internal areas. Most projectiles merely have a two-stage system where the first is triggers upon reaching the target, it softens the target then the second stage penetrates and explodes inside. Smart ones actually have a detection system to explode in the void. Some bunkers were even built with entire rooms filled with equipment and mannequins used specifically to fool advanced weapons systems. The weapon would blow up in those voids instead of continuing into the proper target areas.

>>8166138
>>8166120
>>8166060

>Vacuum would work better than air in spaced armor, but not enough better to justify the hassle of maintaining it. The functional aspect of the spaces is the spaces themselves, not the air that's not worth the effort of keeping out.

>It would have water there or the vacuum of outer space and the function of the product would remain the same.

Do you actually believe that a projectile that weighs probably only a couple ounces, moving at hypersonic velocities is going to be unaffected by whether it's moving through air, water, or a vacuum?

You realize that a shaped charge projectile loses nearly all of its penetrating power over distances measured in feet, right? If they're set off in the open air they'll actually just disintegrate as the tip of the penetrating cone is travelling exponentially faster than the outer edge. That's why they have to put spikes or nose cones on them- to ensure proper standoff distance. Detonating even an inch too early or too late can significantly degrade the performance. That's also why HEAT rounds didn't really take off until after the invention of the piezoelectric fuse.

Air is simply the easiest gas to fill that space with, but the fact that it is a gas is intrinsically important to the design of the armor since after penetrating the outermost plate, the tip of the penetrator is now moving through a material with less resistance than the base is, causing it to break apart much sooner.

>>8166139

>Some projectiles are designed to blow up the instant they reach a void.

In modern production, these are exclusively anti-personnel munitions. APHE projectiles haven't been used as front-line tank munitions since the Korean War.

>>8166222

Why are you lumping this >>8166120 and >>8166139 in with that? It states that the voids' filler doesn't matter. Why reply to it by repeating exactly what it is already stating?

>>8166222
>projectile that weighs probably only a couple ounces
Will be negligibly affected by an inch of air vs an inch of vacuum, with a mass difference of a few milligrams, compared to the several ounces of steel it also has to get through.

>You realize that a shaped charge projectile loses nearly all of its penetrating power over distances measured in feet, right?
Yes. This is mostly due to the internal dynamics of the metal stream rather than aerodynamics (you know, that "the tip of the penetrating cone is travelling exponentially faster than the outer edge" bit). How far do you think a HEAT round would maintain its penetrating power in a vacuum with no fluid resistance at all?

>That's also why HEAT rounds didn't really take off until after the invention of the piezoelectric fuse.
Or, you know, that the importance of the metal liner in a shaped charge wasn't understood until the late 1930s.

>the fact that it is a gas is intrinsically important to the design
So how would the armor performance differ if the spaced armor gap had polyurethane foam or vacuum rather than air? All three have a density far less than the armor layers, and would similarly cause the penetrator stream to break up. It's not the air that matters, but the gap in the dense armor layers.

>>8166273
I bet he'd flip is someone told him about reactive armor and how it works.