Kinetic energy, bulletproof, knifeproof or syringeproof...everyone knows what a bulletproof vest is. But on what physical principle does a "fabric" or a rigid plate stop a bullet or a knife and what is the material that shields you from a penetrating object? What ergonomics, what weight and what benefit/risk ratio is there for the user? What is the (optimal) life span of the protective material? In short, here's a little overview to help you choose the right protection and take into account the constraints that go with it!
Let's start by defining the basics (for those of you who don't like it, go to the next part of the article) - what is kinetic energy? Let's make it simple and brief.

  • It is the energy of a moving body (in this case the bullet, the knife or the syringe). This energy will depend on the mass of the body in question, and its speed. The kinetic energy is measured in joules. In the case of a bullet - which will be the simplest and most meaningful example - it is the kinetic energy released that determines its penetration power (along with a set of other factors such as the caliber of the bullet, its shape, its material, the power of the explosion that will allow the initial force to be imparted - setting the bullet in motion, and the length of the barrel - which will allow the energy to be accumulated up to the muzzle).
  • To calculate the kinetic energy of a bullet (or of another object) it will be necessary to apply the following formula:
  • Ec = 0,5 × m × v 2
  • Ec: Kinetic energy
  • m: mass - in kg
  • v: speed (squared) - in meters (per second, minute, etc.)
    • So for a 9x19mm bullet, with a weight of 8 grams (0,008 Kg) and projected at a speed of 350 m / s it gives:
      • 0,5 × 0,008 (the mass expressed in Kg): 0,004
      • 350 × 350 (the squared speed of the ball in m / s): 122500
      • So: 0,004 × 122500: 490 joules
  • The fascinating thing about energy is that it cannot be lost, but only transferred. Once out of the barrel - and therefore once in the air - the energy of a bullet is subject to friction (by stretching the air) and therefore transfers part of it to the bullet, until it hits its target. At the impact, the remaining energy will be transferred in its entirety (depending obviously on the nature of the target) and will cause the damage that happens to the tissues, the bones, the organs...This is where the bulletproof material will do the job!
The general idea is to absorb (stop the projectile, it's tempting but... you remember that the energy is not lost, it's simply transferred - I'll let you imagine where it would go if the protective material stopped the projectile without absorbing the energy...) the transfer of energy from the projectile to a surface (the largest possible) other than your body. Where it gets complicated is that the tip of a knife or the cone of a bullet have relatively "small" surfaces on impact while concentrating massive energy!

kinetic energy comparison

Ballistic Steel, Kevlar, Goldflex, polyethylene, dyneema, ceramic...Before presenting the mechanical properties of the protection materials, a small list of those used in all the vests of the market (I intentionally leave aside the materials resulting from nanotechnologies, the biosteel - the famous spider silks - or the cellular modifications of the artist Jalila Essaïdi) :

  • Fibers (available in flexible sheets):
    • The para-aramids
      • Twaron (Teijin company)
      • Kevlar (Dupont company)
      • Goldflex (Honeywell company)
    • Polyethylenes
      • Spectra (Honeywell company)
      • Dyneema (DSM company)

Of all these fibers, Goldflex (increased strength, optimal torsional behavior - more expensive to produce) and Dyneema (higher weight/strength ratio than its competitors and remarkable resistance to moisture, abrasion and UV) stand out.

Here again we skip the manufacturing process and the different stages of processing of the fibers, the weaves used, as well as the physical properties of each material or their variations (for your information there are 6 different types of Kevlar, not counting the types of Dyneema, obtained according to a different manufacturing protocol - I do not have enough time to write a book... But if you are interested, send us a message, we will send you the documents)

You will find one of these fibers in all the flexible panels currently available on the market. They have more or less the same mechanical capacities - absorption capacity in joules per m2 - with variations when it comes to resistance to humidity, UV exposure and abrasion. Obviously, some will be "better" than others, but in any case, it should be considered that a damaged plate (following the absorption of a shot, an exposure to a chemical agent, a tear...) must imperatively be replaced.

ballistic fiber dyneema

  • Steels ( in either hard plates or specialised cutouts for vehicle or building protection):
    • Armor or Armox 500 - depending on the manufacturer
      • Without going into details - a steel with a specific structure, used for the manufacture of hard ballistic plates and bullet-proof structures for vehicles, modular buildings... Available in variable thicknesses according to the need.
      • The 500 indication refers to the hardness index (Brinell scale)
      • Steels with an index of 550 or higher are not used for the manufacture of personal protective equipment.
  • Ceramic - or rather a composite material including ceramic (available in hard plates or in marbles, exclusively for bulletproof use):
  • Composed mostly of a first layer of epoxy or fiberglass - protection of the plate against splinters, scratches, blunt shocks ... - ceramic (alumina, boron carbide ...), then layers of polyethylene UHMWPE (ultra high molecular weight polyethylene) or a flexible ballistic fiber (see above) which will ensure the dispersion of energy on the entire surface of the plate. This is what gives us the famous SAPI (Small Arms Protective Insert) ballistic plate.
  • The three ceramic compounds used (most commonly) to make a ballistic protection plate:
    • Aluminum oxide (Al2O3 - commonly known as Alumina)
      • It is the most economical formula (in terms of manufacturing cost and volume of material to be used to obtain an optimal level of protection) and the one with the highest density - depending on the purity of the final product - its manufacturing process must have a purity of 90 to 99,95% and a porosity below 2%
    • Boron carbide (B4C)
      • 2 times harder than alumina, but also with a lower density, it is the ideal material to "stop" a bullet...except that it is expensive to produce, extremely brittle when "torn" - which is the feature of an armor-piercing bullet for example - and that it requires a different manufacturing process depending on whether one wants to obtain optimal protection for the absorption of a single bullet or several. To exploit its exceptional performance, boron carbide is generally used in conjunction with silicon carbide.
    • Silicon carbide (SiC)
      • It has, roughly speaking, the same physical capabilities as boron carbide, but with a higher density. The combination of a hardness almost similar to alumina and boron carbide with its density - depending on the manufacturing process - more or less high, make it the ideal choice for (or rather against) very high speed or armor-piercing bullets.
    • It should be noted that the ceramic component, by nature, is "brittle" and the ceramic protection plate will invariably suffer significant damage on impact - indeed, it is part of what ensures the transfer of energy and the stopping of the projectile. We will discuss the difference between "single" and "multi" hit plate(a plate that has the ability to absorb the energy of a single or multiple projectiles), but as noted in the introduction to the "ceramic" chapter, ensuring the consistency of the material, allowing it to retain its ballistic properties, and avoiding shrapnel projection, is achieved by adding a composite material (covering - epoxy, carbon fiber polyester resins) and a ballistic material (based on polyethylene or aramid fiber for example - allowing the reduction of microcracks in the ceramic plate and an optimal absorption of the kinetic energy). Most ceramic plates also have a layer of material (phenolic foam) for its fire resistance and thermal insulation properties.

Simply put, the stiffer the ceramic plate (and made in conjunction with a "blanket" and "reinforced" with a ballistic fiber), the "harder" the ceramic used - harder than the bullet material - the better!

  • High performance polyethylene (UHMWPE - ultra high molecular weight polyethylene) in its laminated composite form (in its fiber version, UHMWPE is - in particular - the ballistic protection materials Dyneema and Spectra in the form of flexible ballistic plates) - again the material will be used in the form of individual plates or cut to size for the protection of vehicles or aircraft. Let's make it simple: to date it is the most resistant thermoplastic compound (to shocks, solvents, abrasion) and it hardly absorbs humidity. Composed of a series of repeated monomer units (basically the repetition of the structure of a macromolecule - thousands of times. Polymerization), UHMWPE can be manufactured using several processes (with the use of a thermostatic matrix, with a higher or lower number of filaments or a larger or smaller cross-section, with a particular spinning process...) and the protective sheet can have a variable number of sheets (the UHMWPE "sheet" manufactured by DSM Dyneema® SB71, for example), but in the case of a hard sheet it will always be presented in composite form. Its very low density and exceptional strength make it the ideal material for an optimal protection/weight ratio.
  • You will find the UHMWPE in the composition of most ballistic shields and visors - especially because it allows transparency and therefore an optimal vision for the wearer.
  • A UHMWPE plate will not be able to be used for protection against an armor-piercing or high velocity bullet (a bunch of tests have shown this) but will be an excellent additive to the ceramic plate to allow for a sort of individual "sandwich" plate - the ceramic and composite plate as presented above - that will provide protection against most light calibers (excluding some specific ammunition, .50 BMG, .408 CheyTac, basically any anti-material caliber).

ceramic arrangement

Great ! So how does it actually work? Relatively simple! whether it is a fiber, steel or ceramic, the important thing is:

  1. That the molecular structure of the material has a maximum energy absorption capacity.
  2. That the absorption of energy is done on the widest possible surface.
  3. In the case of a bullet-proof vest, the force of the impact on the protective material allows the deformation (and thus reduces the energy concentration by allowing the bullet to expand) or the burst of the projectile.

For the proposed "soft" protective materials (kevlar, goldflex, spectra or dyneema):

For the sake of simplicity, I have deliberately left out the structural differences between para-aramids and polyethylene. Let's imagine a tennis court net (or the net of a soccer field goal). When a ball hits the net, it deforms conically and the strings that make up the net absorb the energy at 360° until it is completely absorbed and the ball stops. The "soft" textile material of a bulletproof plate will act in exactly the same way, except that the trauma caused by a very powerful conical penetration - and over a very small area - to the inside of the body can be just as deadly as if the projectile actually penetrated the body. The difference lies in the fact that the mesh of the fiber is much tighter than the mesh of a sports net. This very fine mesh will allow the energy to be dispersed over the entire surface of the plate and thus reduce the conical deformation imposed on it by the projectile (we will come back to this in the chapter on the various official standards).

To allow this dispersion of energy and the complete stopping of the projectile before penetration, it is necessary that:

  • The layers of textiles that act individually as a net
  • A mesh of each layer that is fine enough for maximum energy dispersion over its entire surface
  • That on impact the energy transfer acts on the projectile itself by "crushing" it to eliminate part of the penetration due to the conical shape of the bullets - and thus by contributing to increase the surface of the bullet's "grip
  • That the fiber used has exceptional tensile strength properties
  • The specific case of knife or syringe guard plates:
  • The difference in velocity (speed) of a stab with a knife (or a spike, or a syringe) is much lower than that of a bullet (even of very small caliber). As a result, manufacturers (the first standardization of anti-knife plates dates back to...1993) have had to adapt the mechanical resistance of the fibers usually used to stop bullets.
  • The fibers used have the same commercial names - Dyneema or Kevlar - but the manufacturing process differs to obtain a mesh capable of absorbing and stopping the progression of a blade or syringe in the surface of the plate.
  • We will come back to this later but it is the English (damn roast beef) that have (in 1993), via the HOSDB (Home Office Scientific Development Branch - the scientific institute of the Ministry of the Interior what) developed a specific standard designed for protection against knife blades or syringes (ballistic capabilities, test protocol, efficiency levels, etc.)
  • It is noted that a knife guard plate may be worn in conjunction with a bullet-proof plate

For proposed "hard" protective materials (ceramics & UHMWPE):

The process is slightly different! The purpose of a hard plate is to protect the wearer from the mechanical damage of a much faster bullet (potentially designed for increased penetration or concentration of kinetic energy on a small area). The behavior of a "smaller" caliber bullet (or one with a smaller initial explosion) upon impact with a "textile" plate will not be at all identical to that of a faster, more "powerful" bullet. On the one hand, because the kinetic energy released could allow the projectile to penetrate the protective surface without any problem - and continue its trajectory through the wearer's body - and on the other hand, because even in the case of energy absorption, the conical deformation imposed mechanically would cause injuries that could be just as deadly as if there were no protection at all. It is therefore imperative that the hard plate:

  • is made of a harder material than the one facing it (the bullet that tries to penetrate)
  • that the energy absorption is done (as for the flexible plates) on a surface as large as possible
  • that on impact (always as for flexible plates) the projectile crushes or disintegrates to the greatest extent possible
  • The particular case of "multi-hit plates" (the plate able to absorb the energy of several projectiles in a row):
  • Nothing very complicated - please refer to the chapter "Ceramics - or rather a composite material including ceramics" which details the structure of a plate consisting of different layers (protective coating - epoxy, ceramic, composite ballistic material and potentially a layer of phenolic foam).
  • It is this "sandwich" composition that will allow to keep mainly the properties of the ceramic (which, as indicated above, will fragment at the first impact). Even in "piece" the ceramic material, as long as the "sandwich" design keeps its initial structure - in two words the ceramic in piece remains compressed in its gangue (before the first impact), will keep its mechanical properties. The composite ballistic material will continue to perform its role as an energy absorber.
  • In addition to the "sandwich" composition, the type of structure used for the ceramic surface is also important. According to the tests mentioned below, it is essential that the ceramic is not laid in one piece but in several "tiles". This tiling allows to keep intact the protection capacities of the tiles adjacent to the tile that absorbed the first impact. Logical.
  • Based on a V50 (velocity 50 - see below) comparison test performed by Messrs Horsfall and Buckley and Watson et al (google it if their tests are of interest to you) with intact and impacted plates, the result indicates (depending on bullet velocity at impact / with 7,62 ammunition / on SAPI alumina plates) a decrease in performance from 3 to 8%. This still shows that the material retains a capacity of 24 to 12% above the requirements of the standard.
  • Please note: even if the material does the job, it won't be able to protect you against dozens of impacts! In two words, take cover!
  • The special case of "stand-alone" plates - that provide the level of protection without being used in conjunction with another (flexible) protective plate:
  • Again, this is a (hard) protective plate that has been manufactured or structured in such a way that it can be used on its own, without being worn in conjunction with a soft plate (typically a protective plate worn in a vest AND a hard plate worn over it in a compartment provided for this purpose). In short, you can use this plate in a tactical "plate carrier" - this will reduce the volume and weight of the vest with soft plate + hard plate combination as well as the wearer's comfort of movement. Obviously this also reduces the surface protection, but if you're pretty sure you're going to face shots of more powerful calibers than those " covered " by a soft might as well not bother - just think of the risk of shrapnel...
  • The "anti-trauma" plate:
  • Simple: it is an additional flexible plate (usually made of fiber, but it has existed in steel or aluminum) that is packaged in a much thinner format than the classic bulletproof flexible plate (but in the same material). The idea is not to offer "additional" protection but to limit the conical deformation on impact (and the resulting physiological trauma) by optimizing the energy dispersion surface and the crushing of the projectile on impact.

But then what type of plates stops what type of calibers or shrapnel?

Each industrialized country - France, USA, Germany, China, Russia, England...has defined, at one time or another, a test protocol that defines the protection capacities (for shrapnel, ammunition, blast effect and knives) of each material used. The different protocols all propose (according to the constraints required for the tests) a scale that allows to determine which product is the most adapted to the risk that we want to cover.

Well, let's start at home, eh? It's the least we can do! The French protocol and assessment scale therefore:

  • Well, there is a slight problem: the AFNOR (Association Française de Normalisation) does not offer a specific protocol for bulletproof materials used for personal protection or on vehicles
  • Note, however:
    • NF A36-800-2 and NF A50-800-2 standards (Hot-rolled weldable steel sheets for shielding - Part 2: fire test method)
    • The standard NF P 78-401 (replaced by the European standard EN 1063 - Glass in building - Safety glazing - Testing and classification of resistance to attack by bullet
    • The NF EN 1522 / 1523 standard (Windows, doors, closures and blinds - Bulletproof - Prescriptions and classification)
    • In short, no comment ...

The American protocol and rating scale:

  • You all know the standard set by the NIJ. But the Yanks like to do things in a big way! This gives :
  1. The standards defined by the NIJ (National Institute of Justice - the US federal scientific research and standards body):

NIJ Standard 0101.07 - Ballistic Resistance (draft)
NIJ Standard 0101.06 - Ballistic Resistance
NIJ Standard 2005 Interim Requirements for Ballistic Resistance
NIJ Standard 0101.04 - Ballistic Resistance
NIJ Standard 0101.04 Revision A - Ballistic Resistance
NIJ Standard 0101.03 - Ballistic Resistance
NIJ Standard 0115.00 - Stab Resistance
NIJ 0104.02 Standard - Riot Helmets and Face Shields
NIJ Standard 010600 - Helmets
NIJ Standard 0117.00 - Public Safety Bomb Suit Standard
NIJ Standard 0108.01 - Ballistic Protective Materials
FBI body armor 2008 test protocol
HP White 401-01b Helmet Testing Procedure

  1. The standards defined by the US military:


The German protocol and rating scale:

  • With my apologies, it is impossible to find a version of the documents in French or English, so I give you the original version in German - you still have to use google translate huh...
  1. The German certification body (Vereinigung der Prüfstellen für angriffshemmende Materialien und Konstruktionen) defined the following standards:

VPAM KDIW2004 Stand: 18.05.2011
VPAM KDIW 2004 Stand: 12.05.2010
VPAM HVN 2009 Booth: 12.05.2010
VPAM APR 2006 Edition: 2009-05-14
VPAM BSW 2006 Stand: 14.05.2009

The Russian protocol and rating scale:

  • The GOST (for those interested in a translation of the document send me a message, we know how to do it internally).

GOST R 50744 95

The English protocol and assessment scale:

  • We recall that the English scientific institute was the first to define a specific protocol for materials manufactured for protection against knives and syringes in 2013.
  1. English certification body - HOSDB (Home Office Scientific Development Branch) defined the following protocols:

HOSDB Body Armor Standards for UK Police (2007)
HOSDB Body Armor Standards for UK Police (2007) 1 Part: General Requirements
HOSDB Body Armor Standards for UK Police (2007) Part 2: Ballistic Resistance
HOSDB Body Armor Standards for UK Police (2007) Part 3: Knife and Spike Resistance

The Chinese protocol and assessment scale:

  • I hope you have some notions of English, this is the only version I found - excluding Chinese and Mandarin of course ...
  1. The standard is defined under the name:

GA 141 2010

NATO Protocol and Rating Scale (STANAG) - for vehicles and aircraft exclusively:

  • This protocol is expressed in 2 volumes (NATO AEP-55 STANAG 4569 1 flight and 2 flight)
  • It is not intended for personal protection elements but exclusively for vehicles and aircraft
  1. The table of the standard is available here:


Australia and New Zealand protocol and rating scale:

  • It should be noted that this protocol only takes into account handguns and hunting caliber .12
  1. The standard is defined under the name:

AS / NZS 2343: 1997



  • Think about mobility and comfort of movement - to be stationary under enemy fire is to be dead
  • No protective material guarantees you that a projectile will not penetrate. Have confidence in your material but in a reasoned way, do not expose yourself in a useless way
  • When a plate (flexible or rigid) has undergone an impact or significant degradation ... it is no longer functional!
  • When you evaluate the weight of your vest or your plates, take into account the weight of your bag, your ammunition, your weapons...
  • Buy "anti-trauma" plates. The cost is lower and in any case less than the pain and the consequent lethal risk of injuries caused by the internal deformation of your flexible plates on impact.
  • Remember that the effectiveness of materials has a lifespan! Beyond the warranty provided by the seller or the manufacturer, you must consider that the material is no longer functional
  • Observe the maintenance and protection instructions (humidity, UV exposure, exposure to solvents, etc.) indicated by the seller or the manufacturer
  • Practice handling your weapons and the accessories you carry with your vest or your plate holder on your back! It will improve your sensations as your reflexes

Good luck, and as always, stay safe, be blessed!

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