Spalling is the exit of glass in transparent armor glazings toward the protected side during an attack, regardless of projectile, blast or forced entry penetration/access. Security glazings can defeat the threat and still allow spalling whether limited or not. Anti-spalling requirements for glazings fall within two levels: Low Spalling (allowing for a limited amount of glazing loss), and No Spalling (allowing for no glazing loss). Spalling can also occur in opaque armors such as steel, aluminum, composites, etc.
At Pinnacle Armor we provide ballistic armor for vehicles, vessels, aircraft, and facilities from .22 caliber up to 30mm cannon. Larger caliber munitions armor is available upon special request. For flexible body armor we provide ballistic resistance from .22 caliber to the .30-06 caliber M2 armor piercing, as well as fragmentation and speciality ammunition like flechettes and specialized sabot projectiles.
The V-50 is a theoretical velocity at which a given projectile (bullet) is going to penetrate the ballistic material 50% of the time and be defeated by the armor material 50% of the time. In tests for flexible ballistic resistant body armor, the projectiles must be stopped with certainty. This means that the vest must be designed so as to have a velocity resistance substantially higher than the ballistic rated limit. For any ballistic resistant material, the higher the V-50 rating, the higher the ballistic protection within a specific level.
The blunt trauma or back face signature/back face deformation is the amount of rearward deformation the body armor will receive when struck abruptly by a projectile (bullet). Although the bullet may not penetrate the soft body armor, the part of the body directly behind the point of impact usually receives a "hammer-like" blow as a result of the deformation of the armor from the impact of the bullet, as it's velocity and energy are dissipated. This blow can produce not only bruises and lacerations to the surface of the skin, but can produce damage to internal organs.
Body armor can achieve proper performance criteria (the preclusion of penetration), however, as most people do not know, the armor can sustain a hit that will deform rearward or push the ballistic panels toward the body up to the allowable depth of 1.73" inches (44mm). This is the maximum amount of blunt trauma allowed by the National Institute of Justice.
A WORD OF CAUTION: Not all the newer, thin, lightweight ballistic grade fabrics pass equally. If the manufacturer passes their testing on a panel in excess of the actual size to be worn on the street, it will exceed 1.73" inches (44mm) on a true vest sized panel. BUYER BEWARE!
If in doubt, request in writing a copy of the passing certifications showing test panel sizes, thickness, number of shots, caliber, type of bullet, and amount of back face signature/deformation.
Yes, the two are very different and are designed to do two very specific functions.
The two functions are:
Due to the physical capabilities of aramid fabrics or aramid composite structures used in each of the above two functions, neither one will work effectively for the other. The reason for this is due to the weave count. Typically fabrics are comprised with a specified crossover weave count that is measured by the square inch. The higher the count the tighter the crimp between crossover points. Stab resistant fabrics rely on extremely tight, closely packed crossover points. When enough layers (plies) of this very tightly wove fabric are combined, resistance to penetration from pointed hand deployed weapons is enhanced.
Three characteristics of a weapon affect it's capability to penetrate something:
Sharp pointed and round objects such as an awl or ice pick have very small pointed tips with little or no surface area to cause resistance. This eliminates the need to forcibly break the fabric fibers, so they merely push the fabric aside and slip through.
Knives not only have sharp pointed tips, but also have sharp cutting edges. The edges also aid in penetration by cutting through the fabric. Especially double edged blades.
Therefore, in stab resistance a very tightly woven fabric of many plies is needed to resist penetration. With enough plies the fabric layup becomes very dense and hard to penetrate for stab resistance only! This type of fabric will fail for ballistic threats as the "fiber crimp" does not allow any elasticity. This is why you don't see many, if any combined ballistic and stab resistance all fabric garments. Those that are available are substantially thicker and heavier incorporating "two vest types" in one.
Pinnacle Armor has compiled a chart that shows the primary testing requirements for ballistics, based on firearm types and calibers. These include data from the United Kingdom, Germany, and the United States.
The basic differences are within three methods of testing. Two utilize various types of explosives, and the other primarily utilizes regulated compressed air. These are further split into two categories: Open Air Arena and Shock Tube Testing.
Open Air Arena tests are conducted in an open field with live explosives detonated at various distances from the test specimen (target). These are conducted on test specimens (in the case of glazings) either mounted into a frame stand or a closed structure replicating a building or similar facsimile. This is the most common method of testing. The tests are conducted with various types of explosives recommended by the manufacturer of the glazings/systems or other government or end users of the product. Each method has its advantages and disadvantages, which are threat specific and based on each product utilized for the testing apparatus and protocol, as well the individual components and assemblies. This becomes evident in the difference between the open air arena cubicle testing and the open air arena frame stand specimen testing. The major difference being that the latter allows for a surrounding of overpressure which aids in mitigating the damage. It is not truly a very good representation as compared to the cubicle. Currently the open air arena testing can provide for greater charge detonation representations than the shock tube systems, and is only limited by open space and charge configurations.
The shock tube testing is conducted in a steel enclosure called a shock tube and can be used with compressed air, fuel air mixtures, or explosives. Compressed air is generally utilized with excellent reproductions of the explosive blast without the expense or associated hazards. The shock tube is similar to a giant CO2 tube attached to a receiving apparatus to hold the test specimens with an attached cubicle to represent a building used to record the resultant damage if applicable. The shock tube utilizes compressed air that is released by bursting a diaphragm releasing the air in an impulse wave similar to that of an explosive blast positive phase shock wave that travels down the expansion chamber to the test specimen where it impacts it. The expansion chamber is similar to a reversed funnel taking the wave from a tube to a full height and width specimen. The atached specimen cubicle catches any broken or shattered glazing and/or framing material and records the resultant overblast pressure and any fragmention debris flying within a "typical" building structure.
The shock tube can readily test rebounding shock waves that are representative of the urban high rise environment in one test, where you would need two time delayed explosive charges in an open air arena to replicate the same. The only drawback to the shock tube tests is that they do not replicate the negative phase as greatly as the open air arena tests. The primary difference other than that, is that the shock tube is not influenced by wind, rain, temperature variances, ground absorption of the detonation, etc. The shock tube focuses 100% of the blast overpressure onto the target specimen.
Any testing category should be selected for the appropriate type of test protocol and procedures as required by either the manufacturers or the end-user requirements.
The typical GSA security criteria for glazing blast mitigation is depicted in the following chart demonstrating the typical protected distance from the window to the interior of the building resulting in 5 blast mitigation levels.
GSA Security Criteria
(Glazing Blast Mitigation Recommendations)