Info Favorites Register Log in
myArmoury.com Discussion Forums

Forum index Memberlist Usergroups Spotlight Topics Search
Forum Index > Historical Arms Talk > Does Armour "Stack"? Reply to topic
This is a standard topic  
Author Message
Matt J.





Joined: 26 May 2010

Posts: 47

PostPosted: Sun 02 Sep, 2012 10:46 am    Post subject: Does Armour "Stack"?         Reply with quote

I'm wondering if the defensive value of armour stacks directly, or if it's more complicated than that.


As an example...

If it took one joule to get a deadly shock through mail, with a warhammer--and, if it takes ten joules to get the same shock through a padded gambeson: Would it take 11 joules to get the same amount of shock through mail with a a padded gambeson?
View user's profile Send private message
Marik C.S.




Location: Germany
Joined: 16 Feb 2010

Posts: 163

PostPosted: Sun 02 Sep, 2012 12:55 pm    Post subject:         Reply with quote

It is far more complicated than that. If it takes 10 joule to get through the gambeson that force is applied in one spot, the spot you hit with your weapon. But the armour spreads the force over a large area of the Gambeson and makes the hit thereby survivable.
Europe - Where the History comes from. - Eddie Izzard
View user's profile Send private message Visit poster's website ICQ Number
Benjamin H. Abbott




Location: New Mexico
Joined: 28 Feb 2004

Spotlight topics: 1
Posts: 1,248

PostPosted: Sun 02 Sep, 2012 1:07 pm    Post subject:         Reply with quote

In The Knight and the Blast Furnace, Alan Williams treats the protection provided by padding as additive. Throughout the book, Williams repeats that padding increases the energy required to defeat any given armor by 50 J.
View user's profile Send private message
Dan Howard




Location: Maitland, NSW, Australia
Joined: 08 Dec 2004

Spotlight topics: 2
Posts: 3,636

PostPosted: Sun 02 Sep, 2012 3:11 pm    Post subject:         Reply with quote

Williams contradicts this himself (pp 943-945)

In one test he measures the amount of energy required for his blade to cut through a certain number of layers of linen in a padded target: 100J – 5th layer; 120J – 9th layer; 140J – 16th layer; 160J – 23rd layer; 180J – 26th layer.
So it took 100J to cut through 5 layers of a 26-layer target

In another test he tells us that it only required 80 J to cut all the way through a 16 layer target.

It seems that the very act of placing the target over additional padding helps to stop penetration of the primary target. I wouldn't be surprised if this difference is noticable no matter what type of armour is tested. It is yet another reason to dismiss all the tests we have seen that don't put some kind of padding behind the armour. Even if the padding itself provides no additional protection (which it obviously does), it seems to improve the defensive capacity of the primary armour as well.
View user's profile Send private message
Timo Nieminen




Location: Brisbane, Australia
Joined: 08 May 2009
Likes: 1 page
Reading list: 1 book

Posts: 1,504

PostPosted: Sun 02 Sep, 2012 4:48 pm    Post subject:         Reply with quote

Yes. The armour being able to move with the impact is the key, as discussed in http://www.myArmoury.com/talk/viewtopic.php?p...ht=#254513

Padding is a good way to get this movement, but there are others. Freely hanging pieces might be even better (e.g., necks, skirts), but that that isn't so useful for torso armour.

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
View user's profile Send private message Visit poster's website
Matt J.





Joined: 26 May 2010

Posts: 47

PostPosted: Sun 02 Sep, 2012 11:46 pm    Post subject:         Reply with quote

Have they created a math formula to simulate this effect? Or, is it still debated...?
View user's profile Send private message
Timo Nieminen




Location: Brisbane, Australia
Joined: 08 May 2009
Likes: 1 page
Reading list: 1 book

Posts: 1,504

PostPosted: Mon 03 Sep, 2012 1:15 am    Post subject:         Reply with quote

A simple treatment of free-to-move armour is easy enough, for penetration by arrows:

Start with the initial energy or speed of the arrow (either will do; they're related). Find the momentum. When the arrow hits the armour, momentum is conserved. That is, the final momentum of the arrow + armour after the impact is the same as the momentum of the arrow before the impact. Calculate the final kinetic energy of the armour - this energy isn't available to penetrate the armour. So, energy available for penetration = initial energy of arrow - final energy of armour.

If it was just a piece of armour floating in empty space, the kinetic energy of the arrow after this impact wouldn't be available either. But the armour will presumably be stopped by padding/backing/laces, so we will keep this energy available.

Example:

100g arrow, 50m/s, kinetic energy E = (1/2) m v^2 = 125J, momentum p = mv = 5Ns.

Hitting a movable 10cm by 20cm iron plate, 1.3 mm thick:

Mass of armour plate = 200g.
Total mass (armour + arrow) = 300g.
Final speed = momentum/mass = 5/0.3 = 16.7m/s.
Energy of armour = (1/2) m v^2 = 28J

So, only 97J is available for penetration, instead of the original 125J. Every bit helps!

More stuff can be included in the model, but this is a reasonable and simple beginning.

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
View user's profile Send private message Visit poster's website
Raman A




Location: United States
Joined: 25 Aug 2011

Posts: 148

PostPosted: Mon 03 Sep, 2012 1:58 am    Post subject:         Reply with quote

the effect is described in physics as impulse

http://en.wikipedia.org/wiki/Impulse_(physics)

its how airbags work. When you're in a car crash the change in momentum you undergo will always be a constant but if you lengthen the time under which your momentum changes (in this case going from a high speed to a stop), you'll be accelerated more slowly. It's pretty intuitive, if one car goes from 0 to 60 in 20 seconds that person will feel a lot more force than someone who accelerates from 0 to 60 in a minute. If you were struck wearing a plate with padding underneath, the padding would crush, lengthening the time that it was under acceleration, lowering the force. That's thinking of it in terms of conservation of momentum.

Thought of another way, in terms of conservation of energy, if you dangle a piece of armor, and strike it with an arrow, a lot of energy would be expended accelerating the armor backwards. If you held it rigid all the energy goes into deforming the material around the area of impact, breaking the bonds with sufficient energy. If there's padding behind armor that gives under an impact, its going to absorb that energy and "waste" it. If the person is accelerated back with the impact that absorbs even more energy. Of course, if the person is moving into the impact then he's adding energy to the collision. Also a really spongy material with a lot of give will make light blows more comfortable, but will flatten almost immediately when struck hard and be virtually useless. This is called bottoming out. A relatively stiff and rigid material that deforms more slowly under high impacts will protect better in those situations, but when hit with a small force they're practically rigid and useless.

the figures Dan Howard quoted make sense to me. It took less energy to cut through more layers of less padding. When you add more padding to change time t in the impulse equation, the force of the blow on the top layers is lowered, and less layers can be cut through even when he applied more energy.

There's a huge amount of research put into this in terms of armor, for military applications as well as for sports such as cycling and football. Modern helmets generally use a combination of soft "low-impact" padding and hard "high-impact" foam. Suspension systems were previously widely used and operate on the same principles but are inferior to modern padding materials.

http://www.bhsi.org/general.htm
this site has a lot of useful information for helmets in general that's easy to understand.

http://www.pas.rochester.edu/~blackman/ur10helmets.pdf
this power point is pretty technical but might have some useful information. A lot of what they model could be applicable to a pollaxe striking a helmeted man in the head.

http://designscience.umich.edu/pdf%20files/APD-2003-05.pdf
This study addresses foam thickness in a helmet. Since the experimental helmet is a steel shell with some amount of foam underneath it, it should be applicable to steel armor with padded backing.

G=C/t where G is peak acceleration during the impact, C is some constant that he calculated using a lot of parameters in his experiment but is specific to whatever helmet and foam he was using, and t is foam thickness.



so according to his research this is how increasing thickness of padding works. Force on y and padding thickness on x. Seems like you get a huge decrease to force with just a small amount of padding, and thicker and thicker padding continues to help but gives diminishing protective returns.

I know that was a long post, hope some of this was useful or relevant to your question, the base line is its really complicated. Researching this stuff is what people do for a living because its still extremely applicable to war, sports, and general safety.

As a side note, I think your example in the original post would actually work out, but only because maille doesn't really do anything in terms of impact protection. It was worn to stop weapons and projectiles from penetrating or cutting the body. In that sense, the only thing protecting from impact would be the padded gambeson.
View user's profile Send private message
Benjamin H. Abbott




Location: New Mexico
Joined: 28 Feb 2004

Spotlight topics: 1
Posts: 1,248

PostPosted: Mon 03 Sep, 2012 8:29 am    Post subject:         Reply with quote

Dan Howard wrote:
Williams contradicts this himself (pp 943-945)


If padding multiplies the energy required to penetrate armor, why does Williams repeatedly treat it as a flat +50 J in examples?

Quote:
In one test he measures the amount of energy required for his blade to cut through a certain number of layers of linen in a padded target: 100J – 5th layer; 120J – 9th layer; 140J – 16th layer; 160J – 23rd layer; 180J – 26th layer.
So it took 100J to cut through 5 layers of a 26-layer target

In another test he tells us that it only required 80 J to cut all the way through a 16 layer target.


That's consistent with how the energy required to pierce iron/steel plate increases by the increase in thickness to the power of 1.6. Hence a 2mm mild steel plate requires 175 J to fully penetrate while 1mm only takes 55 J (this examples suggest the power of 1.67, but Williams uses 1.6 as an approximate standard value). The linen test shows exactly the same exponential increase. 26 divided by 16 equals 1.625, which to the power of 1.67 gives us 2.25. 2.25 times 80 equals 180. This doesn't tell how steel plate and fabric padding interact, though.

Quote:
Even if the padding itself provides no additional protection (which it obviously does), it seems to improve the defensive capacity of the primary armour as well.


There's a Byzantine military manual in I believe Eric McGeer's Sowing the Dragon's Teeth that says as much and emphasizes the importance of padding.
View user's profile Send private message
Ryan S.




Location: Germany
Joined: 04 May 2012

Posts: 353

PostPosted: Mon 03 Sep, 2012 1:34 pm    Post subject:         Reply with quote

a steal plate worn with out padding will stop blows and disperse the energy, but will not absorb the energy. Thus a would be penetrating trauma such as from a sword against sufficient plate will be in effect a blunt trauma. So more armor of any type provides greater protection. It is all about energy, which is why major advancements in weaponry have in many cases dealt with producing and containing greater energy.
View user's profile Send private message


Display posts from previous:   
Forum Index > Historical Arms Talk > Does Armour "Stack"?
Page 1 of 1 Reply to topic
All times are GMT - 8 Hours

View previous topic :: View next topic
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum






All contents © Copyright 2003-2024 myArmoury.com — All rights reserved
Discussion forums powered by phpBB © The phpBB Group
Switch to the Basic Low-bandwidth Version of the forum