Densities of carbon fibers

Eig. 10. The variation of the density of carbon-fiber reinforced epoxy resin with the fiber volume fraction, based on the rule of mixtures. 

Three methods are common, viz, the liquid displacement method, the sink-float method and the density gradient column method. Each of these is a common, standard technique and is fully described in ISO 10119, 1992 (for the determination of the density of carbon fiber), and also in ASTM D 276-87 (reapproved in 1993), which in fact also refers to ASTM D 1505, ASTM D 792, and AATCC, Method 20 (1990) (Fiber identification), each of which deals with the above techniques. ISO 10119 is a very good and concise description of the techniques. However the measurement liquids specified in ISO 10119 of ethanol, methanol, acetone, tricloroethane, and carbon tetrachloride, although suitable for carbon fibers, are not at all suitable for the general range of textile polymers, with the exception perhaps of ethanol and methanol. ASTM D 276 87 recommends the use of / -Heptane for universal application, except, of course for the olefins, such as polyethylene. A range of typical fiber densities is given in Table 4. 

Composite materials that take advantage of the strength, stability, and low density of carbon fibers are widely used. Composites are combinations of two or more materials. These materials are present as separate phases and are combined to form structures that take advantage of certain desirable properties of each component. In carbon composites the graphite fibers are often woven into a fabric that is embedded in a matrix that binds them into a soUd structure. The... 

Figure 5.42 Density of carbon fibers as a function of the density of stabilized fibers obtained from an AN/MA acrylic precursor fiber. Source Reprinted with permission from Takaku A, Hashimoto T, Miyoshi T, JAppI Polym Sci, 30, 1565, 1985. Copyright 1985, John Wiley Sons Ltd.

Figure 17.6 Effect of production temperature on density of carbon fiber.

Low density and high specific strength. The density of carbon fiber is one quarter of steel s and a half of aluminum alloy s, but its strength is 16 times more than steel s and 12 times more than aluminum alloy s ... 

Carbon Composites. In this class of materials, carbon or graphite fibers are embedded in a carbon or graphite matrix. The matrix can be formed by two methods chemical vapor deposition (CVD) and coking. In the case of chemical vapor deposition (see Film deposition techniques) a hydrocarbon gas is introduced into a reaction chamber in which carbon formed from the decomposition of the gas condenses on the surface of carbon fibers. An alternative method is to mold a carbon fiber—resin mixture into shape and coke the resin precursor at high temperatures and then foUow with CVD. In both methods the process has to be repeated until a desired density is obtained. 

Low density, carbon fiber-carbon binder composites are fabricated from a variety of carbon fibers, including fibers derived from rayon, polyacrylonitrile (PAN), isotropic pitch, and mesophase pitch. The manufacture, structure, and properties of carbon fibers have been thoroughly reviewed elsewhere [3] and. therefore, are... 

Detailed accounts of fibers and carbon-carbon composites can be found in several recently published books [1-5]. Here, details of novel carbon fibers and their composites are reported. The manufacture and applications of adsorbent carbon fibers are discussed in Chapter 3. Active carbon fibers are an attractive adsorbent because their small diameters (typically 6-20 pm) offer a kinetic advantage over granular activated carbons whose dimensions are typically 1-5 mm. Moreover, active carbon fibers contain a large volume of mesopores and micropores. Current and emerging applications of active carbon fibers are discussed. The manufacture, structure and properties of high performance fibers are reviewed in Chapter 4, whereas the manufacture and properties of vapor grown fibers and their composites are reported in Chapter 5. Low density (porous) carbon fiber composites have novel properties that make them uniquely suited for certain applications. The properties and applications of novel low density composites developed at Oak Ridge National Laboratory are reported in Chapter 6. 

Morpholine chromate, molecular formula, properties, and uses, 6 562t Morphology. See also Structure of carbon fibers, 26 737-739 of high density polyethylene, 20 162 of polymer blends, 20 356 of polymer colloid, 20 386-388 of PVC particles, 25 658-661, 661-663, 664-665... 

Preparations of carbon fibers are similar to those of GC, with two important exceptions caused by the small fiber diameter. Fibers are mounted quite differently from GC, particularly for in vivo applications that require a small overall electrode diameter. In addition, fibers can experience much higher current densities during electrochemical pretreatment, which can qualitatively alter ECP effects. 

A composite sample of carbon fiber and epoxy weighs 2 g. When the sample is submerged in water (density = 1 g/cm ), its weight is 0.633 g. The weight of the fibers is 0.966 g after the epoxy is degraded with concentrated nitric acid. Calculate (a) the volume fraction of fibers, (b) the density of the composite, and (c) the volume fraction of voids. 

Boron fibers have at their core a tungsten (ca. 12 to 15 pm in diameter) or carbon fiber, which serves as a substrate during manufacture. Due to the high density of tungsten (19.3 Mg/m- ), a fiber thickness of 100 to 200 pm is necessary to achieve a low overall density for the fiber (ca. 2.6 Mg/m ). Therefore, latterly deposition on carbon fibers (density 1.8 Mg/m, diameter 8 to 10 pm) has been favored. This development has been driven by their commercial availability of carbon fibers. In addition to their low density (ca. 2.0 to 2.3 Mg/m- ) these fibers exhibit a low surface roughness and low internal stress. 

Radiation vulcanization of carbon fiber reinforced styrene-butadiene rubber causes a substantial increase in crosslink density (Figure 11.4) and tensile strength (Figure 11.5). This magnitude of change is possible only when the interaction between the filler and the matrix is improved. When irradiated in the presence of air, carbon fibers gain functionality which substantially increases their adhesion resulting in a spectacular improvement in properties. SEM studies show that as the dose of radiation increases, the adhesion of the... 

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