Aramid Kevlar

Fig. 4. Specific properties of reinforcing fibers for composite materials. K-29 and K-49 represent Kevlar aramid fibers. Other designations are explained...

Warner, Steven B. (1995). Fiber Science. Englewood Cliffs, NJ Prentice Hall. Yang, H. H. (1993). Kevlar Aramid Fiber. New York John Wiley. 

Following the technological breakthroughs which led to the discovery of (1) the liquid crystalline behavior ofpara-oriented aramids26 and (2) a novel method for spinning anisotropic liquid crystalline polymer solutions,27 Kevlar aramid fiber was produced and commercialized by the DuPont company in 1972. Other fibers based on aromatic polyamide compositions, which were produced and commercialized by other companies, were Technora (Teijin, Japan), Teijinconex (Teijin, Japan), andTwaron (Akzo, The Netherlands). Additionally, SVM is a fiber produced in the Former Soviet Union and it was announced in 1990 that a new aramid fiber had been introduced by Hoechst, in Germany. 

Figure 4.19 Different forms in which Kevlar aramid fiber is available pulp, floe, staple, and continuous fiber woven into a variety of fabrics (courtesy of Du Pont).

Kevlar aramid fiber has good vibration damping characteristics. Dynamic (commonly sinusoidal) perturbations are used to study the damping behavior of a material. The material is subjected to an oscillatory strain. We can characterize the damping behavior in terms of a quantity called the logarithmic decrement, A, which is defined as the natural logarithm of the ratio of amplitudes of successive vibrations, i.e. 

Reinforcement of epoxy, polyester, and other resins for use in aerospace, marine, automotive and sports industries. We have previously mentioned the vibration damping capacity of Kevlar aramid fiber. Layers of woven Kevlar are used in skis for damping purposes and, of course, to reduce the weight. Kevlar is used as a protective sheath in fiber optic wave guides and to reinforce optical fiber cables because of its high tensile modulus and strength, and low electrical conductivity. 

Kevlar 29 and versions thereof (K 129 and Kl j.) are also used extensively in lightweight body armor as well as composite liners (with vinylester, polyester or epoxy as the matrix). A quick look at the properties of different Kevlar aramid fibers in Table 4.2 shows why K29 is better than K49 for lightweight body armor applications. K29 has a higher strain to failure than K49. That means that the total work of fracture, i.e. the area under the stress-strain curve, is larger for K29 than K49. Hence, the energy absorbed in the fracture process is higher for K29... 

Figure 4.29 (a) A helmet reinforced with Kevlar aramid fiber and a bullet resistant vest made of Kevlar aramid fiber. 

F ure 4.29 (b) Lightweight armor products made of Kevlar aramid fiber... 

Sinclair (1950) devised this loop test to estimate the strength and elastic modulus of fibers. There are many variants of this test, which is basically a kind of bend test. Greenwood and Rose (1974), among others, used such a test to evaluate Kevlar aramid fiber. Huttinger (1990) used such a loop or knot test to determine the deformation characteristics of carbon fibers. Figure 9.5 shows the knot test schematically. If d is the fiber diameter and is the loop diameter corresponding to a tensile strain of e in fiber, then we can write... 

The body armor described here is constructed of DuPont Kevlar Fabric. This cloth is woven from strands of Kevlar Aramid Fiber, a material developed by DuPont as a replacement for steel wire belted radial tires.This material is lighter than ballistic nylon and pound for pound it s several times as strong as steel. When Kevlar is used in multiple layers, it can effectively stop bullet penetration and greatly reduce internal injuries from blunt trauma. Finished armor pads are light, flexible and easily concealed. 

A. General Info The flexible armor pad insert is made from 8 layers of DuPont Kevlar Aramid Fabric.Two types of Kevlar cloth are appropriate for use in soft body armor. 

H. H. Yang, Kevlar Aramid Fiber, Wiley, Chichester, 1993. 

Research and development in fluid jet technology led to its widespread use in film and web processing, mixers, reactors, and fiber processing. Applications to fibers alone includes Taslan bulked yams, jet piddlers, draw-jets, interlaced yams, bulk-crimped carpet fibers (BCF), and spunbonded products such as Reemay polyester, Typar polypropylene (PP), and Tyvek olefins. New fibers also were introduced Nomex aramid, especially suited for high-temperature applications Lycra spandex, an elastic textile yam Qiana nylon, with a silklike appearance and Kevlar aramid, used in products ranging from tires to bullet-resistant vests. 

Experiments were carried out with low molecular weight poly(p-phenylene terephthalamide) (PPTA) produced by the acid degradation of commercial Kevlar aramid fibers (6N HCl, 20 hr). The inherent viscosity of the degraded polymer was ca. 1.0 which, based on an empirical correlation between molecular weight and inherent viscosity, corresponds to a molecular weight of ca. 

The corresponding linear aromatic polyamide is Kevlar aramid which decomposes only above 500°C (Equation 2.37). 

Anonymous. Kevlar aramid fiber. Technical Guide H-77848 4/(X), DuPont Advanced Fibers Systems, Richmond, VA, 2(X)1. 

Source From DuPont Technical Guide for Kevlar Aramid Fiber, H-77848, 4/00 DuPont Technical Guide for Nomex Brand Aramid Fiber, H-52720, 7/01 Teijin Ltd., Teijinconex Heat Resistant Aramids Fiber 02.05 Teijin Ltd., High Tenacity Aramids Fibre Technora TIE-05/87.5 Akzo Nobel, Twaron—Product Information Yarns, Fibers and Pulp. 

DuPont Technical Guide for Kevlar Aramid Fiber, H-77848, 4/00. 

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