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Old 08-13-2022, 01:28 AM   #1
StevenH
 
Join Date: Feb 2008
Location: Portland, Oregon
Default Cut resistance of various materials

I have been trying to find the cut resistance of various fabrics (linen, cotton, silk, spidersilk, Elven silversilk, etc).


I was able to find the statistics for Cut-Tex:
Fabric Weight

  • 447gsm (grams per square metre)
Protection Levels

  • EN ISO 13997 (TDM-100 Test) Cut Resistance Level E = 26.4 Newtons
  • ISO 13997:1999 Blade Cut Resistance Level 5 = 26.4 Newtons
  • ANSI/ISEA 2016 Blade Cut Resistance Level A5 = 2681 grams/force
  • EN388:2003 (coupe test) Cut Resistance Level 5 = 26.4 Newtons
  • EN 388:2016 Tear Strength Level 4 = 518.2 Newtons
  • EN 388:2016 Abrasion Resistance Level 3 = More than 2,000 cycles
  • EN 388:2016 Puncture Resistance Level 4 = 271.6 Newtons
But without knowing what the numbers are for "mundane" fabrics, it doesn't tell me much. And googling it wasn't helpful either, as I wasn't able to find any specific info.



So, if I wanted to make a gambeson out of Cut-Tex, for instance, what would it's DR be? Layering 20 some-odd layers of linen gives about DR 3.

But I can't find the cut resistance levels of linen, so I lack the context necessary to extrapolate the cut-tex version.



Anyone have a source for finding this information?
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Old 08-13-2022, 08:19 AM   #2
Varyon
 
Join Date: Jun 2013
Default Re: Cut resistance of various materials

I'm afraid I can't help with finding the values you're looking for, but UHMWPE (the base for Cut-Tex, according to the website) is listed in "Cutting Edge Armor Design" (Pyramid #3/85) as Ballistic Polymer, which is probably close enough to model Cut-Tex (Cut-Tex may not be quite as protective, as from the website it sounds like it's designed to be more usable for clothing - including surviving multiple wash cycles - but should be close enough). Ballistic Polymer has a maximum DR (at 1/2" thick) of 24/9.6 (I believe you'd round the latter down to 9; this is DR 24 vs pi/cut, 9 vs everything else), and Torso armor (or Torso+Groin if using the armor divisions from Basic Set rather than those of Low Tech and the armor design articles*) made at that thickness would weigh right around 10 lb (10.08 lb); something like a gambeson, covering that as well as the arms down to the hands, would weigh twice as much, so 20 lb (technically, 20.16 lb).

You probably aren't going to make a gambeson that thick, as above 1/4" thick it isn't flexible by GURPS rules. Something like DR 10/4* is more likely (and note that * designation means it is treated as GURPS flexible), which would weigh in at around 4.2 lb for Torso protection, 8.4 for a long-sleeve gambeson.
EDIT: For reference "Low Tech Armor Design" (Pyramid #3/52) has Cloth armor (which would include linen) as having a maximum DR (at 1") of 4. DR 3 cloth armor is a full 3/4" thick, and is rigid - not appropriate for a gambeson. A gambeson is more likely around DR 1* (flexible), and a long-sleeve version of that would be around 11.9 lb, nearly 1.5x the weight of the above armor of comparable thickness (this gambeson would be 1/4", the thickest you can get and still be flexible; the above DR 10/4* gambeson would be a bit over 1/5").

*GURPS 4e originally treated Torso and Groin as two separate hit locations, with armor that only covers the upper torso designated as Torso and those that covered the entire torso as Torso + Groin. Low Tech changed this - it divided Torso into two hit locations, Chest and Abdomen, and made Groin a sublocation of the latter; the armor design articles in Pyramid are based on the LT rules. Roughly speaking, pre-LT Torso armor would be Chest armor in LT, while pre-LT Torso+Groin armor would be Torso (Chest+Abdomen) armor in LT.
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Last edited by Varyon; 08-13-2022 at 08:28 AM.
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Old 08-13-2022, 09:25 AM   #3
Anaraxes
 
Join Date: Sep 2007
Default Re: Cut resistance of various materials

Quote:
Originally Posted by StevenH View Post
Layering 20 some-odd layers of linen gives about DR 3.
Probably not a terrible comparison, actually.

This is an example of the cotton fabric that's used as the control standard in the EN 388 cut resistance test. As you can see, it's a fairly lightweight sort of cotton canvas.

The actual cut test involves counting the number of turns of a circular blade necessary to cut the material under test (determined by when the blade makes electrical contact with a conductive material under the test sample). The control fabric is a "1". The blade count gets transformed into a scale value from 1-5 using the Speed/Range Table table below:
  1. 1.2 turns
  2. 2.5 turns
  3. 5 turns
  4. 10 turns
  5. 20 turns
The other kind of cut test (both ANSI and EN 388, when the material is such that it dulls the circular blade) involves a razor blade that slides 20mm on the fabric with some weights piled on top (figuratively speaking) until it cuts through (making electrical contact like the other test). This kind of test is a direct measurement, so it doesn't have any standard reference material that it has to be compared to -- which is unfortunate for our purpose, since that also deprives us of any means of comparison other than to modern work gloves.

But here are some leather (cowhide, goatskin) gloves from one manufacturer with their ANSI cut resistance levels, so you can at least make some visual comparison. It's possible to hit the A9 level with relatively form-fitting gloves, but I can't tell by looking how stiff or thick they are. But just based on looks, I'd say they don't exceed the standard GURPS equipment list gloves by much, if anything. Probably spot them DR 3, matching the "Sharp-Protective Gloves" listed on HT69.

As Varyon mentioned, I don't think the materials are engineered so much to have a maximum armor value as they are for other practical considerations, like flexibility/touch sensitivity, durability, and ability to be cleaned. The maximum level on the ANSI scale, 9, equals 6000 grams of force* on that razor blade. It's hard for me to imagine any sword strike that doesn't have at least 60 N behind it, though the armor would certainly be good for all the glancing blows and partial parries and such that wind up being modelled in GURPS as low damage rolls.

--
* Yeah, I know

Last edited by Anaraxes; 08-13-2022 at 09:40 AM.
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