Aramids mechanical properties

Aramid Fibers. Aromatic polyamide fibers exhibiting a range of mechanical properties are available from several manufacturers, perhaps the best known being Du Pont s proprietary fiber Kevlar. These fibers possess many unique properties, such as high specific tensile strength and modulus (see Fig. 4). Aramid fibers have good chemical resistance to water, hydrocarbons, and solvents. They also show excellent flame retardant characteristics (see High PERFORMANCE fibers Polyamdes). 

Fluoroelastomers Novikova et al. [32] reported unproved physico-mechanical properties of fluoro mbbers by reinforcement with chopped polyamide fibers. Other fiber reinforcements are covered by Grinblat et al. [33]. Watson and Francis [34] described the use of aramid (Kevlar) as short fiber reinforcement for vulcanized fluoroelastomer along with polychloroprene mbber and a co-polyester TPE in terms of improvement in the wear properties of the composites. Rubber diaphragms, made up of fluorosilicone mbbers, can be reinforced using aramid fiber in order to impart better mechanical properties to the composite, though surface modification of the fiber is needed to improve the adhesion between fluorosUicone mbber and the fiber [35]. Bhattacharya et al. [36] studied the crack growth resistance of fluoroelastomer vulcanizates filled with Kevlar fiber. 

Aramid fibers, 13 372-373, 395 asbestos substitute, 3 314t chemical resistance of, 19 731t consumption of, 19 735t mechanical properties of, 13 376 properties of, 1.9 729-7301 as reinforcement materials, 26 756, 760 Aramid films/papers, properties of, 1.9 7331 Aramid polymer device, 16 1 Aramid products, economic aspects of,... 

Aramid fibres have high specific mechanical properties and are used for their attractive characteristics such as ... 

Brown, J.R., P.J.C. Chappell, Z. Mathys (1992b). Plasma surface modification of advanced organic fibers, part III. Effects on the mechanical properties of aramid/vinylester and extended chain polyethylene/ vinylester composites. J. Mater. Sci. 27. 6475-6480. 

Figures 9.19 and 9.20 present a survey of the mechanical properties of some (unidirectional) composites, in comparison with some other materials. In Figure 9.19 the values of modulus and strength are plotted as such, while in Figure 9.20 these values have been divided by the specific mass. From Figure 9.20 the enormous advantage of composites with respect to stiffness and strength per unit weight, in comparison to metals, is clearly visible. The modem carbon and aramide composites are superior to those based on glass fibres, for the specific stiffness even by a factor between 4 and 5.

The mechanical properties of paracrystalline aramides and other high-performance polymeric fibres are shown in Table 19.11. In comparison some other fibres are mentioned in this table (see also Sect. 13.6). Aramide fibres display a very high refractivity (refractive index and strong birefringence // 2.2, n 1.6). 

High performance polymer fibers (HPPF) have excellent mechanical properties compared to traditional textile fibers such as nylon. The typical HPPFs are aramid and polyethylene fibers (6). Aramid is a generic name for a class of aromatic polyamide fibers, most of which are varieties of poly(p-pheny-lene terephthalamide). Kevlar is the trade name of the varieties of aramid polymers introduced conunercially by Dupont. The molecules in the fibers of these materials are oriented in the axial direction. Poly(p-phenylene terephthalamide) is a rigid molecule with the following structure ... 

Table 4 compares the mechanical properties of various organic fibers, graphite/carbon fibers, ceramic fibers, and glass fibers, and lists commercially important applications. One major application of organic fibers, such as Spectra and aramid fibers, is in ballistic In contrast, graphite, ceramic fibers, and glass fibers are primarily used in structural applications. One of the reasons that organic fibers find little... 

The high moisture absorption of aramid fibers is their biggest disadvantage. It was reported in the literature that moisture absorption by epoxy laminates degrades their mechanical properties. ° ° Hygroscopic fibers provide an easy route for moisture ingress. The addition of aramid fibers to epoxy and phenolic composites slightly improves their flame resistance and decreases smoke formation. ... 

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