Continuous fibers aramid

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).

The FRPs for demanding structural applications comprising continuous p-aramid fiber reinforcements are most frequently based on epoxy matrices [54-56]. The main reasons... 

The term reinforced plastic (RP) refers to composite combinations of plastic, matrix, and reinforcing materials, which predominandy come in chopped and continuous fiber forms as in woven and nonwoven fabrics. Other terms used to identify an RP include glass fiber reinforced plastic (GFRP), aramid fiber reinforced plastic (AFRP), boron fiber reinforced plastic (BFRP), carbon fiber reinforced plastic (GFRP), graphite fiber reinforced plastic (GFRP), etc. 

For a wide range of apphcations, composites reinforced with continuous fibers are the most efficient structural materials at low to moderate temperatures. Consequently, we focus on them. Table 5.3 presents room-temperature mechanical properties of unidirectional polymer matrix composites reinforced with key fibers E-glass, aramid, boron, standard modulus (SM) PAN (polyacrylonitrile) carbon, intermediate modulus (IM) PAN carbon, ultrahigh modulus (UHM) PAN carbon, ultrahigh modulus (UHM) pitch carbon, and ul-trahigh thermal conductivity (UHK) pitch carbon. The fiber volume fraction is 60 percent, a typical value. 

Even though reinforcement efficiency is lower for discontinuous than for continuous fibers, discontinuous and aligned-fiber composites (Figure 16.8ii) are becoming increasingly more important in the commercial market. Chopped-glass fibers are used most extensively however, carbon and aramid discontinuous fibers are also used. These short-fiber composites can be produced with moduli of elasticity and tensile strengths that approach 90% and 50%, respectively, of their continuous-fiber counterparts. 

Aramid (Kevlar 49) continuous-fiber, epoxy prepreg 75.00-100.00 66.8... 

Composites. The history of phenoHc resin composites goes back to the early development of phenoHc materials, when wood flour, minerals, and colorants were combined with phenoHc resins to produce mol ding compounds. In later appHcations, resin varnishes were developed for kraft paper and textile fabrics to make decorative and industrial laminates. Although phenoHcs have been well characterized in glass-reinforced composites, new developments continue in this area, such as new systems for Hquid-injection molding (LIM) and sheet-molding compounds (SMC). More compHcated composite systems are based on aramid and graphite fibers. 

Many different thermosetting polymers are used in pultmsion, eg, polyester, vinyl ester, epoxy, and urethane. Reinforcements must be in a continuous form such as rovings, tows, mats, fabrics, and tapes. Glass fibers are the low cost, dominant composition, but aramid and carbon fibers are also used. 

The reinforcements amenable to RTM are similar to those used for pultrusion, except that they need not be continuous in nature. Thus, E-glass, S-glass, aramid, and carbon fibers are commonly used, as are discontinuous filaments such as wood fiber and polyesters. Even metal and ceramic fibers can be used in this technique. In one method, the preform is fabricated by spraying 12- to 75-mm-long chopped fiber rovings onto a preshaped screen. A binder sprayed with the fibers keeps them in place and holds the preform shape, which is then placed in the mold. 

Composite In polymer technology a combination of a polymeric matrix and a reinforcing fiber with properties that the component materials do not have. The most common matrix resins are unsaturated thermosetting polyesters and epoxies, and reinforcing fibers are glass, carbon, and aramid fibers. The reinforcing fibers may be continuous or discontinuous. Some matrix resins are thermoplastics. 

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