History and Useful Information
BODY ARMOUR TODAY
Myth and Misconceptions by A. W. Hellweg
Body armour is nothing new. Ancient warriors have worn bronze, copper and iron breast plates as far as recorded history. During World War II flack jackets were introduced and by the Vietnam war nylon filled jackets were issued to troops. Unfortunately, the jackets were very bulky and rather hot.
In the early 1960s DuPont was driven by two goals – to create a fibre with the heat resistance of asbestos and stiffness of glass. A breakthrough occurred in 1965 when Stephanie Kwoek, a research scientist at the DuPont Experimental Station in Wilmington, found that pare aminobenzoic acid could be polymerized and solubilized under special conditions to yield a rigid spinnable polymer. And so was the super fibre which we know as KEVLAR discovered. KEVLAR is now used world wide by manufacturers in the production of soft body armour and in many hard armour applications.
Today we use a second generation KEVLAR. This is referred to as KEVLAR 129 and it is 15% stronger, 15% lighter and 20% thinner and softer than the original KEVLAR. This allows the manufacture of lighter weight personal body armour which is more wearable.
There are other materials available that are used in soft body armour that are cheaper than KEVLAR, but incurring some trade off in regard to weight, comfort and/or bulk.
To begin to understand how KEVLAR works, imagine several wooden sticks. With your fist you can break them one at a time. If they are tied together in a bundle, none can be broken. When KEVLAR is woven as a cloth and layered, a bullet encounters many threads at once. The denser the weave (the more threads per unit area) the more resistance the bullet encounters.
Understanding this, we can understand some other properties of KEVLAR body armour. A small bullet fired at KEVLAR encounters fewer threads than a large bullet. A fast small bullet with the same total energy of a large slow bullet will penetrate body armour much deeper. A .357 magnum from a revolver is therefore easier to stop than a .22 magnum from a rifle. Additionally, the harder bullets do not deform on impact as much and penetrate more that softer bullets. A deformed bullet will encounter more KEVLAR and is more likely to be defeated.
Stopping the bullet is only part of the problem. As KEVLAR does not stretch, when a bullet is contained, the energy is absorbed and dispersed from the struck fibres to other fibres in the weave of the fabric and ultimately to the body. This shock to the body is know as blunt trauma and must be kept at a level where injury from it does not occur. The human body can withstand a certain amount of blunt trauma and this tolerance to it is referred to in millimetres of “back face signature” during testing of body armour.
There are numerous different test standards around the world. The oldest and best known standard is by the U.S. National Institute of Justice and know as N.l.J. 0101.03. This standard allows for a back face signature of 44mm when body armour is tested. This is regardless of level of protection the body armour offers. Other standards used, such as the U.S. PPAA Standard 1989-05 also use 44mm as the maximum allowable blunt trauma, but requires less shots fired against the armour being tested. Some armour that passes for instance the PPAA standard may still fail the NIJ standard during testing.
As there is a lot of confusion about the various test standard, the harder NIJ standard is used by law enforcement agencies in the USA and generally in other countries which do not have their own test standards. In Australia, where there is no Australian standard, all body armour tendered for and also sold under contract by us to various Police and Government Departments MUST meet the NIJ standard. The NIJ standard is also required by all of our Asian and Middle East customers. In Europe we work manly to the German standard Schutzklasse “L” which allows only 40mm blunt trauma for concealment vests (Covert Armour) and 20mm blunt trauma for any type of vest which is worn over clothing (Overt Armour). In Finland where personal body armour is issued to every police officer the NIJ standard is used. In Great Britain we work to the Home Office requirement of 25mm blunt trauma using the NIJ test standard. This clearly demonstrates, that the NIJ Standard and its test method is most widely used standard in the world.
There are basically six protection levels under the NIJ standard ranging from Level I for .38 revolver to Level IV for .30-06 Armour Piercing Rifle Ammunition and allows to test with any type of ammunition using the prescribed test methods. There are only five levels under the PPAA standard available, as this standard does not have a Level I for .38 revolver. The main level of protection used in Australia by Police Forces is Level III-A, as protection is required against the .22 magnum rifle. This round must not be confused with the .22 LR which is a much slower round and not metal jacketed. The .22 magnum is a widely used round in Australia and as it is a metal jacketed fast moving bullet, it is not easy to stop. However, with the new KEVLAR 129 type cloth stopping .22 magnum is not a problem and the armour is even lighter and more flexible than before. Level Il-Plus Covert Armour manufactured by us has the critical area of the front and rear of the vest reinforced to withstand any attack from .22 magnum and also from the more powerful .44 magnum. Also stopped are 9mm submachine guns in these areas, even though the armour is only referred to as a Level Il-Plus vest.
We have been supplying Australian Police and Government Departments since 1982 with body armour, all tested to NIJ standards. We are Australia’s oldest body armour manufacturer and the only DuPont selected and approved body armour manufacturer in. This accreditation is only given to manufacturers who produce body armour to extremely high quality standards and stringent specifications which is complemented by our five million dollar Product Liability Insurance cover.
There is a lot of myth and misinformation being spread on body armour in regard to test standards, weight, water resistance, UV light, perspiration and comfort. The weight of a vest will vary according to its protection level and to body area covered. When comparing weight of body armour of the same level of protection from different manufacturers, one must first establish the weight per square meter of the armour. This is the only way to compare weight of body armour, as the more body area that is protected, the weight of the garment will increase. The smaller the body armour panels, the lighter the weight. Also the finer the fibre, the lighter the fabric. Fibres are measured in deniers. A 750 denier fabric is much lighter and softer than a 1420 denier fabric, but also more expensive. Other factor that contributes to weight are the use of other materials than KEVLAR, such as Ballistic Nylons and other substitutes, which require more layers of fabric to achieve the same thread level.