Standards, Part 2: Fe, F.I.E., fo, fum!

This is the continuation of my last post, regarding standards and homologation of safety equipment.

In the HES world, one of the more commonly quoted homologations is that granted by the Federation Internationale d’Escrime (FIE) for sport fencing equipment (masks and clothing in particular). Because of its prevalence, let’s dig into it a bit.

The FIE’s body for homologation is referred to as the Committee for Electrical Apparatus and Equipment (SEMI), and they are the organization to whom manufacturers submit documentation to obtain approval for a given product. Part of this documentation package is the report from a specific testing institute detailing the results of tests per CEN EN13567, level 2 (Protective clothing - Hand, arm, chest, abdomen, leg, genital and face protectors for fencers - Requirements and test methods), a roughly 50 page document. In other words, we have a CEN standard that is the basis of the FIE homologation process. Level 2 simply refers to the specific values that need to be met in the tests (there is a level 1 with less stringent requirements).

Let’s look at a couple of different pieces of fencing equipment that are relevant to HES: masks and clothing (jackets and pants/knickers). For each you will often see a value, such as 1600N on masks, quoted. What is this value? For both masks and clothing, it is a reference to the penetration resistance testing done as part of the homologation process. 1600 N is 1600 Newtons, or approximately 360 lbs-force. Sounds good right? Well, now it’s time to ask some questions and talk some mechanics:

1. Where is the force measured?
2. How is the force determined?
3. What are the limits on the force for homologation?
4. What about the mesh of the mask?

I am going to address each of the above in turn, in the order above because I think it will be the clearest way. Before I get started, I want to be clear: this penetration test is not the only test performed, but it is the one with a number that is visibly attached to the masks.

Where is the penetration force measured on the garments and masks? 

These details are in EN13567, section 5.10.5: high-velocity penetration test for garments and mask bibs. The section states that 10 circular samples of 65 mm diameter (~2.5 inches) of the areas to be tested are cut from the provided sample garments, which had been stored in a prescribed manner for 24 hours prior to test (temperature 20 °C and relative humidity 65%). So to be clear: for masks that quoted number is only for the bib. It says nothing at all about the mesh itself. For garments, essentially the entire front and appropriate weapon side is considered in the zone of protection, with exceptions for waistbands, knickers cuffs, etc.

How is the force determined? 

Per EN13567, section 5.10.5, there are 3 types of acceptable apparatus (I’m not giving exact quotes here, this is just to give the idea):

• High-velocity constant rate compression tester with a force transducer (device for measuring force, usually attached to a computerized data acquisition system) attached to the moving penetrator.
• Drop-rig with the penetrator and force transducer attached to a falling mass
• Drop-rig with a force transducer attached to a fixed penetrator and the fabric sample holder attached to a falling mass.

In all three devices, the moving component must reach a velocity of 6-8 m/s (19.6-26.2 ft/s), in the drop-rig devices the falling mass must be at least 5 kg-f (11 lbs-f).  The penetrator described by the standard consists of two parts: a mounting section and the penetrating section. The penetrating section is a 30-50mm long x 3 mm wide square section with 0.5mm radius corners, and a pyramid section point with an included angle of 120°.  The sample holder is a cylinder with a threaded locking collar arrangement that will allow the cloth sample to be securely fastened by the locking collar, such that there is no slippage of the fastened cloth sample. The standard requires that the penetrator contact the center of the sample within 1mm. The force (presumably peak force, though it is not specified) reported by the transducer at penetration is recorded for each sample, and this value used for comparison to the levels within the standard.

If we look at this test, it is pretty well described. Assuming you have the equipment, it would be possible to perform the test based on the information contained in the standard. To put some of the numbers in perspective, the drop-rig systems require a rig with a height of greater than 1.8m (5.9 ft), and the energy at time of impact will be at least 90 joules.  To put this into perspective, the SCA rapier marshal’s handbook (dated 2006) refers to a bench test with a dropped mass and penetrator to certify clothing that uses a minimum of 1.5 joules and a 4mm round penetrator (flat face). The FIE’s rules are much more stringent in this regard.

What limits does the FIE put on the penetration for garments and bibs? 

For bibs, the high-speed penetration lower limit is 1600 N. For garments, the high-speed penetration lower limit is 800 N. For reference, the rapier rules for the SCA stipulate 550 N rated garments (at a lower impact energy than the FIE tests), which lies about halfway between CEN performance levels 1 and 2. The calibration fabric referenced in EN13567 (two layers of roughly 16 oz cotton canvas, layered such that there is a 45° angle between their warp angles) has a penetration force of roughly 645 N, with a higher impact energy than the SCA test.

What's the deal with the 12 kg punch test? 

I want to first discuss the ubiquitous ‘12 kg punch test’ that often comes up with regards to masks. After that, I’ll get back into the homologation requirements based on EN13567.

The 12 kg punch test as used in sport fencing (and SCA rapier combat) is intended to be a sort of go/no-go gauge, a field test that can be performed quickly and easily to determine if the mesh of a mask is ‘acceptable’. There are three components:

1. The assumption that the mesh was acceptable when manufactured/purchased
2. That a visual inspection for damage has been performed
3. The actual punch test.

The first part is implicit, but important: the 12 kg punch test is meant as a simple test that can be performed at an event on a questionable mask. Therefore, if the mask does not appear questionable (hence the visual inspection), it will not be tested as it is assumed to be adequate. There in general doesn’t appear to be a standing rule to test all masks every time (in sport fencing or the SCA rapier rules)– looking through discussion boards for both, as well as the rules, there appears to be a great deal of personal discretion on the part of event officials in how often the test is performed.

The actual punch test is performed with a relatively small hand-held device that has been calibrated to allow the operator to apply a force of approximately 12 kg-f (~118 N or ~25 lbs-force) through a small conical penetrator that is meant to nestle into the mesh without penetrating or spreading the mesh apart (if it does, this is deemed a failure). There are a few points to note about this test. First, because no specific fixture is specified (some discussion boards and instructions recommend holding it between your legs snugly, but without deforming the mask), you may have a good deal of variation between tests. Second, the pass-fail criteria are largely based on fairly subjective observation (do you see penetration, dents or damage to the mesh), and the tester does not have a fixed speed. Ideally, the test would be ‘quasi-static’, meaning that the load is applied very slowly. One final issue with the test is that it may cause damage to the mask, depending on how it is performed, and that damage may not be immediately observable. These issues are among the likely reasons why this test is not part of the homologation process.

To put the 12 kg-force value into perspective, CEN standard EN13567, section 4.8.2 (level 2) requires that the penetrator described above for the clothing tests, when applied in a gap of the mesh at the front of the mask at a speed of 100 mm/min (.0017 m/s, about four thousand times slower than the high-speed tests for clothing discussed earlier – this qualifies as quasi-static) does not penetrate at or below 1000 N (~102 kg-f). In other words, in a far more robust and repeatable test, the FIE masks are required to resist penetrations applied with over eight times more force than the 12 kg punch test. So while a failure of the 12 kg punch is likely the mark of mask that is dangerous to use, a mask which passes it may still fall far below the FIE homologation value.

What are the FIE homologation requirements for masks?

Standard EN13567 has quite a bit of detail to it, covering both pure metal mesh masks and partial transparent plastic masks. Sections 4.7.2 and 4.8.2 discuss materials, while sections 5.8, 5.10.3, and 5.10.4 deal with the test procedures. For masks, a combination of materials for the ‘hard shell’ (essentially everything that isn’t the bib) is possible, as is the use of perforated material, so long as a 2.1 mm round probe and a 0.2x4mm flat probe cannot pass through any aperture in the protected area manually. This probe test should also pass if the mask is compressed on the sides at 900 N, or vertically at 900 N, and after compression no fracture or failures of joints should be evident. For a level 2 steel mesh the specified material is a stainless steel wire of 1mm diameter, assembled into a mesh with holes less than 2mm square. For padding, the standard calls out that the “thickness and compressibility of padding or the properties of any other system shall be limited so that under foreseeable impacts the mask does not move significantly onto the user's head with the consequence that their nose might contact the hard shell”.  The tests that homologated masks are required to pass include (beyond the bib penetration tests discussed earlier):

• Material-level mechanical testing of mesh materials (bending and tensile testing, microstructural characterization)
• Vertical pull test to ensure that mask cannot be pulled off of a human head with a 20 N (~4.5 lbs-force) vertical load
• Horizontal push test to ensure that the mask face cannot be brought into contact with the wearer’s face with a 50 N (~11 lbs-force) horizontal load delivered at eye-level on the front of the mask
• Bib attachment testing (tension on the bib center, pull down and toward the back from the ‘chin’ of the mask at 45 degrees to the horizontal) with a ramped load of 800 N (~180 lbs-force) over 20-60 seconds, holding at 800 N for 5 seconds.
• Low-velocity (quasi-static) penetration test for the hard-shell, performed in at least 6 specific locations (more if the hardshell includes a visor of a separate material). Penetration must not occur at or below 1000 N and permanent deformation at the contact point must be less than 10 mm to achieve level 2 certification.
• Impact test for the hard-shell, which uses a guided mass of 1.5 kg (including penetrator) falling from a sufficient height to deliver 8.5 J at impact (compare to the ~90 J test of the bib). The test is performed at a number of specific locations, similar to the low-velocity test. 

The next part will talk more about how the FIE homologation rules can be of use to us in the HES world.