Armour pentration and Armour resistance

[Paullus Scipio]

I am posting this on a new thread, because for reasons unknown the thread of this name seems to be closed.
Could a moderator look into this, please, and then transfer this across?

Following on from my earlier post, and keeping in mind that kinetic energy and momentum are the key , but not the only, factors that defensive armour has to defeat we can move on to a detailed study.
First, some important notes so that we don’t get too carried away with what is for many, a fascinating subject.
• Since the dawn of time there has been a constant duel between armour/weapons, that is still going on today. From time to time, one or the other gains the advantage (e.g the rise and domination of armoured infantry in greek/roman times, the era of the longbow/crossbow, the brief reign of ‘hardened’ plate , which I guess is the subject of Alan Williams “The Knight and the Blast Furnaceâ€

[Paullus Scipio]

By way of contrast to the above figures, here are some which I think come from Alan Williams "The Knight and the Blast Furnace".
Alas, where they are quoted no context is given and as we have seen, that makes all the difference.

5mm cuir-boulli requires 20 joules for spear/lance to penetrate, or 50 joules with a blade stab.90 joules for a sword cut/slash
10 mm cuir-boulli, increased to 30 joules for spear/lance and 90 joules for blade stab.
!.9 mm munition plate ( i.e. not especially hard ) 100 joules for spear/lance, 190 joules for blade stab
mail - 120 joule to pierce
Layered linen ( in view of Dan Howard's posts, presumably loose /quilted and not glued ?? )
5 layers -100 joules
9 layers -120 joules
16 layers- 140 joules
23 layers- 160 joules
26 layers -180 joules

There seems to be something suspiciously high about the latter figures, and Williams has been criticised for being "armour biased" and under estimating weapon force and kinetic energy ( but I believe most estimates/trials/calculations are probably too high for real battle conditions.
Perhaps Dan and others with access to this source can elaborate for us ?
What were the conditions of these figures? Practical tests ?( and if so, quasi static or dynamic or both ) Calculated/estimated ? ( if so, then to be treated with great caution ).
If the figures are appropriate, then the ones for linen give food for thought.
If hoplite tube-and thorax corselets were made of this, then in the light of Blyth's figures, the protection was way more than adequate, and there would have been no need to re-inforce them with scales etc against Persian archery. Similarly, if linen was this effective, then given its other advantages ( lightness etc ) why was it not more widely used ??

We need to know more !

[Sean Manning]

By way of contrast to the above figures, here are some which I think come from Alan Williams "The Knight and the Blast Furnace".
Alas, where they are quoted no context is given and as we have seen, that makes all the difference.

5mm cuir-boulli requires 20 joules for spear/lance to penetrate, or 50 joules with a blade stab.90 joules for a sword cut/slash
10 mm cuir-boulli, increased to 30 joules for spear/lance and 90 joules for blade stab.
!.9 mm munition plate ( i.e. not especially hard ) 100 joules for spear/lance, 190 joules for blade stab
mail - 120 joule to pierce
Layered linen ( in view of Dan Howard's posts, presumably loose /quilted and not glued ?? )
5 layers -100 joules
9 layers -120 joules
16 layers- 140 joules
23 layers- 160 joules
26 layers -180 joules

There seems to be something suspiciously high about the latter figures, and Williams has been criticised for being "armour biased" and under estimating weapon force and kinetic energy ( but I believe most estimates/trials/calculations are probably too high for real battle conditions.
Perhaps Dan and others with access to this source can elaborate for us ?
What were the conditions of these figures? Practical tests ?( and if so, quasi static or dynamic or both ) Calculated/estimated ? ( if so, then to be treated with great caution ).
If the figures are appropriate, then the ones for linen give food for thought.
If hoplite tube-and thorax corselets were made of this, then in the light of Blyth's figures, the protection was way more than adequate, and there would have been no need to re-inforce them with scales etc against Persian archery. Similarly, if linen was this effective, then given its other advantages ( lightness etc ) why was it not more widely used ??

We need to know more !

Williams' figures were based on experiments. Unfortunately, he is often a bit vague about the details of tests other than the world-class ones he did on metal plate.

Williams tested a 32-layer linen jack section with a density of about 1 g/cm^2- this is heavy, so apparently it was densely stitched, heavy linen. Those figures are how many layers were penetrated at a given energy, which is different from how much energy would be needed to penetrate as many layers by themselves. I think the test was with a blade rather than a spike or point, but can't find my notes.

Williams' figures for jack penetration fit a very nice linear curve, with each layer absorbing about 4 J. I think they are accurate, but high end. I think it would be easier to penetrate a ten-layer jack of a given cloth than to cut through ten layers of a twenty-layer jack because the back layers add "give" and reinforcement.

Linen was widely used! In the middle ages after AD 1000, for example, cloth armours were the standard medium-cost equipment of common soldiers. Cloth armour is not, as far as I know, lighter than plate armour giving similar overall protection.

I'm not sure if scale-reinforced armour was a reaction to Persian archery as Blyth suggests. It might have been fashion, or inspired by desire for better protection from spears. I haven't read his thesis.

[Paullus Scipio]

A most enlightening post, Sean.
Judging by Blyths figures,see above, the difference in force between a stab with a spear and a sword are not great, but Williams shows that the energy required to penetrate (which is not the same thing as Blyth was measuring ) has significant differences.
The rather high figures he gives for the Jack would be consistent with his other tests if made with a blade.
And you make two further good points - textile armour is not necessarily lighter than metal for a given level of protection, and use of textile (and leather for that matter ) was widespread in the Middle ages.
I was however thinking more of Graeco/Roman times - the use of textile/leather armours, even in Hellenistic armies, dies out shortly after mail appears which might seem unlikely if a multi-layer Jack offered such good protection as the raw figures suggest. But judging by Williams other figures, it would appear that a lower energy would be required from a spear/javelin, and much lower still from an arrow.
We should also remember that 'effectiveness' is not the only, nor even the main criteria for choosing armour.As you have pointed out, even fashion can be a criteria.
However, in the case of the tube-and-yoke corselet, the scale re-inforcements can hardly be as a reaction to spears, which had been around for a long time and which the 'Hopla' had evolved to resist, and it is stretching co-incidence that the scales appear around the Persian wars, particularly in Attic pottery and die out shortly after them. While they might be a fashion, copying asiatic enemy styles, it is surely stretching co-incidence again that scales very effectively increase resistance to arrows?