thompsonx
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Joined: 10/1/2006
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ORIGINAL: BamaD
I was surprised when I learned this too.
Kevlar is constructed on a principal much like chain mail. As you may know it stopped some types of weapons very well and others such as arrows very poorly. It will stop a blunt object well as it slows it down. You can still get broken ribs from a large bore hand gun at close range, most rifle rounds will go through the level of armor street cops wear and since a knife depends on a point (particularly when stabbing) it is fairly useless. As for links just google kevlar,virtually any site that tells about it will confirm everything I said. For anyone who knows much about guns (gun nuts to you) this is basic common knowledge, slightly more obscure than which end the bullets come out of.
Do you just open your mouth to take a shit?
Stab armor and combination stab-ballistic armor[edit]
Early "ice pick" test[edit]
In the mid-1980s the state of California Department of Corrections issued a requirement for a body armor using a commercial ice pick as the test penetrator. The test method attempted to simulate the capacity of a human attacker to deliver impact energy with their upper body. As was later shown by the work of the former British PSDB, this test over stated the capacity of human attackers. The test used a drop mass or sabot that carried the ice pick. Using gravitational force, the height of the drop mass above the vest was proportional to the impact energy. This test specified 109 joules (81 ft·lbf) of energy and a 7.3 kg (16 lb) drop mass with a drop height of 153 cm (60 in).
The ice pick has a 4 mm (0.16 in) diameter with a sharp tip with a 5.4 m/s (17 ft/s) terminal velocity in the test. The California standard did not include knife or cutting edge weapons in the test protocol. The test method used the oil/clay (Roma Plastilena) tissue simulant as a test backing. In this early phase only titanium and steel plate offerings were successful in addressing this requirement. Point Blank developed the first ice pick certified offerings for CA Department of Corrections in shaped titanium sheet metal. Vests of this type are still in service in US corrections facilities as of 2008.
Beginning in the early 1990s, an optional test method was approved by California which permitted the use of 10% ballistic gelatin as a replacement for Roma clay. The transition from hard, dense clay-based Roma to soft low-density gelatin allowed all textile solutions to meet this attack energy requirement. Soft all textile “ice pick” vests began to be adopted by California and other US states as a result of this migration in the test methods. It is important for users to understand that the smooth, round tip of the ice pick does not cut fiber on impact and this permits the use of textile based vests for this application.
The earliest of these “all” fabric vests designed to address this ice pick test was Warwick Mills’s TurtleSkin ultra tightly woven para-aramid fabric with a patent filed in 1993.[50] Shortly after the TurtleSkin work, in 1995 DuPont patented a medium density fabric that was designated as Kevlar Correctional.[51] It should be noted that these textile materials do not have equal performance with cutting-edge threats and these certifications were only with ice pick and were not tested with knives.
Knife standards developed by HOSDB-Stab and Slash[edit]
Parallel to the US development of “ice pick” vests, the British police, PSDB, was working on standards for knife-resistant body armor. Their program adopted a rigorous scientific approach and collected data on human attack capacity.[52] Their ergonomic study suggested three levels of threat: 25, 35 and 45 joules of impact energy. In addition to impact energy attack, velocities were measured and were found to be 10–20 m/s (much faster than the California test). Two commercial knives were selected for use in this PSDB test method. In order to test at a representative velocity, an air cannon method was developed to propel the knife and sabot at the vest target using compressed air. In this first version, the PSDB ’93 test also used oil/clay materials as the tissue simulant backing. The introduction of knives which cut fiber and a hard-dense test backing required stab vest manufacturers to use metallic components in their vest designs to address this more rigorous standard. The current standard HOSDB Body Armour Standards for UK Police (2007) Part 3: Knife and Spike Resistance is harmonized with the US NIJ OO15 standard, use a drop test method and use a composite foam backing as a tissue simulant. Both the HOSDB and the NIJ test now specify engineered blades, double-edged S1 and single-edge P1 as well as the spike.
In addition to the stab standards, HOSDB has developed a standard for slash resistance (2006). This standard, like the stab standards, is based on drop testing with a test knife in a mounting of controlled mass. The slash test uses the Stanley Utility knife or box cutter blades. The slash standard tests the cut resistance of the armor panel parallel to the direction of blade travel. The test equipment measures the force at the instant the blade tip produces a sustained slash through the vest. The criteria require that slash failure of the armor be greater than 80 newtons of force.[53]
Combination stab and ballistic vests[edit]
Vests that combined stab and ballistic protection were a significant innovation in the 1990s period of vest development. The starting point for this development were the ballistic-only offerings of that time using NIJ Level 2A, 2, and 3A or HOSDB HG 1 and 2, with compliant ballistic vest products being manufactured with areal densities of between 5.5 and 6 kg/m² (1.1 and 1.2 lb/ft² or 18 and 20 oz/ft²). However police forces were evaluating their “street threats” and requiring vests with both knife and ballistic protection. This multi-threat approach is common in the United Kingdom and other European countries and is less popular in the USA. Unfortunately for multi-threat users, the metallic array and chainmail systems that were necessary to defeat the test blades offered little ballistic performance. The multi-threat vests have areal densities are close to the sum of the two solutions separately. These vests have mass values in the 7.5–8.5 kg/m² (1.55–1.75 lb/ft²) range. Ref (NIJ and HOSDB certification listings). Rolls Royce Composites -Megit and Highmark produced metallic array systems to address this HOSDB standard. These designs were used extensively by the London Metropolitan Police Service and other agencies in the United Kingdom.
Standards update US and UK[edit]
Metropolitan Police officers supervising World Cup, 2006
As vest manufactures and the specifying authorities worked with these standards, the UK and US Standards teams began a collaboration on test methods.[54] A number of issues with the first versions of the tests needed to be addressed. The use of commercial knives with inconsistent sharpness and tip shape created problems with test consistency. As a result, two new “engineered blades” were designed that could be manufactured to have reproducible penetrating behavior. The tissue simulants, Roma clay and gelatin, were either unrepresentative of tissue or not practical for the test operators. A composite-foam and hard-rubber test backing was developed as an alternative to address these issues. The drop test method was selected as the baseline for the updated standard over the air cannon option. The drop mass was reduced from the “ice pick test” and a wrist-like soft linkage was engineered into the penetrator-sabot to create a more realistic test impact. These closely related standards were first issued in 2003 as HOSDB 2003 and NIJ 0015. (The Police Scientific Development Branch (PSDB) was renamed the Home Office Scientific Development Branch in 2004.[55]
Stab and spike vests[edit]
These new standards created a focus on Level 1 at 25 joules (18 ft·lbf), Level 2 at 35 J (26 ft·lbf), Level 3 at 45 J (33 ft·lbf) protection as tested with the new engineered knives defined in these test documents. The lowest level of this requirement at 25 joules was addressed by a series of textile products of both wovens, coated wovens and laminated woven materials. All of these materials were based on Para-aramid fiber. The co-efficient of friction for ultra high molecular weigh polyethylene (UHMWPE) prevented its use in this application. The TurtleSkin DiamondCoat and Twaron SRM products addressed this requirement using a combination of Para-Aramid wovens and bonded ceramic grain. These ceramic-coated products do not the flexibility and softness of un-coated textile materials.
For the higher levels of protection L2 and L3, the very aggressive penetration of the small, thin P1 blade has resulted in the continued use of metallic components in stab armor. In Germany, Mehler Vario Systems have developed sophisticated hybrid vests of woven para-aramid and chain mail their solution was selected by the London Metro Police. Another German company BSST, in cooperation with Warwick Mills, has developed a system to meet the ballistic-stab requirement using Dyneema laminate and an advanced metallic-array system, TurtleSkin MFA. This system is currently implemented in the Netherlands. The trend in multi threat armor continues with requirements for needle protection in the Draft ISO prEN ISO 14876 norm. In many countries there is also an interest to combine military style explosive fragmentation protection with bullet-ballistics and stab requirements.
http://en.wikipedia.org/wiki/Bulletproof_vest#Stab_armor_and_combination_stab-ballistic_armor
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RE: Kajime powells death by cop caught on tape - 
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I will remember to bring a comprssion bandage. 
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