Brief introduction of ballistics

Ballistics is the science of studying material behavior under stress generated from impact by projectiles at high speed, like a bullet or shrapnel from an explosion. This allows for the evaluation and development of protection materials based on test results and research. Searching on the matter of armored vehicles, you will most definitely come across terms like FB 6 / BR6 / VR 6, or you might see some manufacturers stating that their vehicles are VR7 certified. It is useful to understand what these acronyms stand for. Abbreviation “FB” is defined in the standard DIN EN 1522 and is used to indicate the protection level of opaque (non-transparent) materials, such as armor steel, kevlar, twaron, aramid, UHMwPE (Ultra High Molecular weight Polyethylene like Dyneema or Spectra), ceramic etc. Abbreviation “BR” is defined in the standard DIN EN 1063 and is used for protection levels of transparent armor (bullet-proof glass). Abbreviation “VR” is defined in the standard BRV 1999 (the newest edition is BRV 2009) and specifies protection level of a complete vehicle. A European body VPAM – Vereinigung der Prüfstellen für angriffshemmende Materialien und Konstruktionen (Association of Centers for Certification of Bullet-resistant Materials and Constructions) – defined 14 protection levels instead of 7 levels as were defined by the standards EN 1522 / EN 1063. A correspondence of these classifications is shown in the table below:

What is ballistic testing

Ballistic testing means to take a protection material such as armored steel, bullet proof glass (to be correct it’s called multilayered laminated glass but the more common name is bullet proof), and make it undergo a test of impact of certain ammunition type, to be accurate one must understand that protection depends basically on the ammunition type not the type of weapon, because nowadays there are several ammunition types for almost every weapon, For example the AK47 has Soft core bullet (SC)

Hard core bullet (HC), armor piercing incendiary bullet (BZ) ,They all come out from the same weapon but differ vastly in characteristics, so it has to be stated that the protection level provides protection against the following weapon with this specific caliber. Another thing to notice that stating only the caliber doesn’t cut it out, because you can find same caliber shot from different weapons, having different characteristics, lots of different parameters play role in determining the ballistic characteristics of some kind of ammunition, to name a few is the muzzle speed, weight of the projectile, material of the bullet, shape of the bullet and etc.

In the armored cars field testing a very important factor is the kinetic energy of the projectile and the angle of impact, which both are closely related, test is to be performed under 90 degrees angle, in which position the bullet has the maximum impact energy, if the angle is less than 90 degrees then there is a great possibility of ricochets.

Bullet-resistant glass or transparent armor materials (BR)

This kind of materials is made using a multi-hit capability from components such as polycarbonate, or by using layers of laminated glass. The main need of these materials is the ability to pass light like standard glass but in the same time provide protection from fragmentation or ballistic impacts with minimized distortion of vision. The Transparent armor is often made by sandwiching layers of regular glass and adding plastic to provide impact-resistance. The glass which is much harder than plastic flattens the bullet and thereby prevents penetration, while plastic elasticity and adhesion prevents glass layers from shattering. There is some factors must be taken into consideration to understand the nature of these material such as thickness and weight and space, more thickness will increase the ballistic performance but it will increase weight and will need more space to install.

Non transparent materials (FB)

This kind of materials don’t have the property of transmitting rays of light through its substance, like armored steel, ceramics, providing covering used to prevent damage from being inflicted to an object. This kind of materials can be certificated through different certificates; Different factors determine the ability of armored steel sheets to correspond to ballistic threads like thickness and distance of shouting.

Composite materials

Composite materials are formed by combining two or more materials in such a way that the constituents of the composite materials are still distinguishable, and not fully blended. Like fiber, ceramics, in armored cars industry main advantage of these materials is weight savings and high level of resistance to threats.

VR

VR is the European standard for armored vehicles, it means the combination and incorporation of materials into the vehicle body and the structure, there is a whole science dedicated to structural integrity.

VPAM

Association of testing institutes for attack-protection materials established (VPAM) to create standard guidelines for the qualification of ballistic materials. Test Houses at Mellrichstadt, Munich, Ulm Vienna, and other European institutions are accredited under the VPAM. There’s a lot of confusion because of the introduction of the new standards VPAM: The point is that the most popular protection class for civil vehicles – B6 –became VPAM 7 and B7 became VPAM 9. Hence it can only be advised to pay attention to what standard – BRV1999 or BRV2007 – is referred to. Other points to watch out are excluded rounds from the test procedures, like “FB4 without FB3”, “FB7 without AP bullets” or limited conditions of the tests, like “FB6 without car-body (soft skin) effect” or “B7 at 45 degrees obliquity angle”. Another issue is that VPAM does not require registering yaw angle. Yet the tests without measuring yaw angle cannot be representative – depending on the projectile, with yaw angle more than 7 degrees the density of the kinetic energy can be up to 20% less, which obviously is a significant deviation from the test conditions.

Din

A standard issued by German Institute for Standardization is the German national organization for standardization, covers Bullet proof glass resistance.

STANAG 4569

Standard issued by NATO standardization agreement covering the standards for the “Protection Levels for Occupants of Logistic and Light Armored Vehicles”. Was suggested to consolidate different threats for meaningful comparison, STANAG 4569, in this specification, lightweight protection against common threats used against NATO forces is desired. The threats are segregated into 5 levels of increasing magnitude. In order to support material development in this area, composite armor made from S-2 Glass fibers and phenolic resin has been tested against the range of threat levels that this specification encompasses. At the low threat levels, fiberglass composite armor alone defeats the threat; however, at the higher threat levels, a multi-component armor made with a facing material is required. The threats listed through the use of traditional monolithic metallic armor systems. These systems are quite well understood, and could easily be adapted to any of the new vehicles under development. The problem is that in order to defeat modern threats, which are becoming more and more lethal, a tremendous amount of the traditional armor is required.

Standard of Safety for Bullet-Resisting Equipment UL762

Issued by Underwriters Laboratory (the nation’s leading third-party product safety certification agency). Few companies actually have their materials tested by the Underwriters Laboratory. Instead they turn to a dedicated materials lab that scrupulously follows the UL standard. In the case of UL 752, the material to be tested is securely mounted 15 feet from the muzzle of the test firearm (which is itself locked into a bench rest). A clean piece of 1/8th-inch-thick corrugated cardboard (called a “witness plate”) is mounted 18 inches behind the test piece. The witness plate is checked after each shot in order to indisputably establish not just whether or not the bullet beat the barrier (which tends to be pretty obvious), but also whether there was any spalling.

The eight levels of UL-rated bullet resistance are broken into three groups, each with its own protocol:

LEVEL 1 THROUGH 3 BULLET RESISTANT GLASSES For Level 1 through Level 3 bullet resistant glass (meant to protect against 9mm, .357 Magnum, and .44 Magnum rounds), a fresh sample must stop: * Three shots within a 4-inch triangle with no spalling on the “protected” side * Three shots within a 1.25 to 1.75-inch area (some spalling is acceptable) * One unsupported edge shot (some spalling is acceptable here, too)

LEVEL 4 AND 5 BULLET RESISTANT GLASS Level 4 or 5 bullet resistant glasses are meant to stop a single shot from a .30-06 or AK-47 assault rifle, respectively. Samples must stop: * One center shot * One unsupported edge shot (some spalling is OK)

LEVEL 6 THROUGH 8 BULLET RESISTANT GLASSES

These levels of security are intended to stop bursts from submachine guns and assault rifles, such as UZIs, M16s, and AK-47s. Level 6 through 8 bullet resistant glass must stop: * Five shots within a 4.5 inch square You might assume that a bullet resistant system made from UL-rated materials is as bullet resistant as its component pieces. Nonetheless any assembly sold as having a given “UL-rating” must be independently tested under laboratory conditions and meets the UL specification.

National Institute of Justice (NIJ)

Issued an evaluation program to provide lightweight, concealable body armor to a test pool of American law enforcement officers to ascertain if everyday concealable wearing was possible. This standard is applicable to all ballistic resistant materials (armor) intended to provide protection against gunfire. Many different types of armor are now available that range in ballistic resistance from those designed to protect against small caliber handguns to those designed to protect against high powered rifles. Ballistic resistant materials are used to fabricate portable ballistic shields, such as ballistic clipboards for use by a police officer, to provide ballistic protection for fixed structures such as control rooms or guard stations, and provide ballistic protection for the occupants of vehicles.

Correspondence of diff classes Each class of armoring has different correspondence, some of them can hold a variety of ammunition type some type may leave injuries for example a vpam10 standard car can hold a 6 kg TNT under the wheel blast and guaranty a full safety for passengers but car with vpam7 will not guarantee the same level of safety.

B standards – did not include Kalashnikov B standards didn’t include Kalashnikov because it’s an European standard, so B standard didn’t measure the effects of Kalashnikov.Temperature of the glass

The value of a resistance changes with changing temperature of bullet proof glass, but this is not as we might expect, mainly due to a change in the dimensions of the component as it expands or contracts. It is due mainly to a change in the resistivity of the material caused by the changing activity of the atoms that make up the resistor. The reasons for these changes in resistivity can be explained by considering the flow of current through the material. The flow of current is actually the movement of electrons from one atom to another under the influence of an electric field. Electrons are very small negatively charged particles and will be repelled by a negative electric charge and attracted by a positive electric charge. Therefore if an electric potential is applied across a conductor (positive at one end, negative at the other) electrons will “migrate” from atom to atom towards the positive terminal. Only some electrons are free to migrate however. Others within each atom are held so tightly to their particular atom that even an electric field will not dislodge them. The current flowing in the material is therefore due to the movement of “free electrons” and the number of free electrons within any material compared with those tightly bound to their atoms is what governs whether a material is a good conductor (many free electrons) or a good insulator (hardly any free electrons). The effect of heat on the atomic structure of a material is to make the atoms vibrate, and the higher the temperature the more violently the atoms vibrate.

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