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Kevlar (para-aramid) [2] is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora.Developed by Stephanie Kwolek at DuPont in 1965, [3] [2] [4] the high-strength material was first used commercially in the early 1970s as a replacement for steel in racing tires.
A call for a next generation plate, to stop even greater velocity threats than the ESAPI plate was issued by the U.S. Army in 2008. [5] The X Threat Small Arms Protective Insert plates are specifically allowed scalar or flexible systems, and asked for better coverage, with less than a pound of additional weight.
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Excellent thermal stability at temperature extremes, water repellency, chemical stability and resistance to petroleum products have made Kevlar KM2 an indispensable asset to the military personnel who use it every day." [1] "Kevlar KM2 fiber is a transversely isotropic material. Its tensile stress–strain response in the axial direction is ...
Numbering the carbon atoms sequentially around a ring, para-aramids have the linkages attached at positions 1 and 4, while meta-aramids have them at positions 1 and 3. [7] That is, the attachment points are diametrically opposite each other in para-aramids, and two atoms apart in meta-aramids. The illustration thus shows a para-aramid.
Nomex is an example of a meta variant of the aramids (Kevlar is a para aramid). Unlike Kevlar, Nomex strands cannot align during filament polymerization and have less strength: its ultimate tensile strength is 340 MPa (49,000 psi). [2] However, it has excellent thermal, chemical, and radiation resistance for a polymer material.
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/m 2 (1.1 and 1.2 lb/ft 2 or 18 and 20 oz/ft 2). However police forces were evaluating their "street ...
Although the tensile strength is similar to Kevlar, Vectran still tends to experience tensile fractures when exposed to significant stress.The wispy, hair-like fibers tend to fray, to easily acquire dirt, and to readily entangle in hook-and-loop fasteners, from which they must sometimes then be cut or (when possible) torn. [2]