Processing of carbon fibers

Polyacrylonitrile (PAN) precursor fibers are more expensive than rayon. Nevertheless, PAN is more commonly used because the carbon fiber yield is about double that from rayon. Pitch-based carbon fibers are also important, because, potentially pitch is perhaps the cheapest raw material. Table 8.2 shows that carbon yield is highest from the mesophase pitch. The reader is cautioned that this is true only if we exclude the losses during the mesophase conversion step. If, however, one compares the overall carbon fiber yield from raw pitch to that from PAN, then the yield from PAN is higher. In any event, the carbon fiber yield or precursor weight loss is a very important factor in the economics of processing. 

There are certain essential steps common to all processes of carbon fiber manufacture. These are  

Polyacrylonitrile (PAN) is the most common precursor used to make carbon fibers. A flow diagram showing the steps involved in making PAN-based carbon fiber is shown in Fig. 8.3. The PAN precursor has a flexible polymer chain structure like any other polymer, but it has an all carbon backbone chain that contains polar nitrile groups, as shown in Fig. 8.4. During the stabilization treatment, the PAN precursor fiber is heated to 200-220 C, under tension. When this is done oxygen is absorbed, and it serves to cross-link the chains the fibers turn black, and a stable ladder structure is formed. A ladder polymer is a rigid 

Manufacturer Trade name Young s modulus, 1 (GPA) Tensile strength, tr (GPa) Strain to failure, e (%) 

Pitches form an important and low cost raw material for producing carbon fiber. There are three common sources of pitch  

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Fig. 7. Processing of carbon fibers from mesophase pitch.

Table 4.1 shows some of the parameters and properties of the most common carbon fiber paper materials being produced commercially for use in PEM and DLFCs. Figure 4.3 shows an SEM (scanning electron microscope) picture of a carbon fiber paper without any coating. In the following subsection we will briefly discuss the fabrication process of carbon fibers and carbon fiber papers. 

The uniformity of the field emission image was greatly improved by means of preliminary plasma-chemical processing of carbon fibers bundle. 

Qui, D., and Pantano, C.G., Sol-gel processing of carbon fiber-reinforced glass matrix, in Ultrastructure Processing of Ceramics, Glasses and Composites, J.D. Mackenzie and D.R. Ulrich, Eds., John Wiley Sons, New York, 1987. 

From this point of view, improved carbon fiber properties are to be expected from the fibers with highest apparent shrinkage force, where the loss of attained molecular order by relaxation is the lowest. This may be an additional reason for the good performance of the AN/VBr precursor. In fact, the carbon fiber properties of this precursor are the best of those compared in Table 13. However, there is no clear trend relating properties to shrinkage force. As discussed in the preceding sections, the whole process of carbon fiber making is too complex to expect a simple relationship. 

ZSIGMOND B., HALASZ L., CZVIKOVSZKY T., EB processing of carbon fiber reinforced braided composites, Radiat. Phys. Chem., 67, 441 - 445, 2003. 

Isaac DH, Ozbek S, Francis JG, Processing of carbon fibers Texture enhancement induced by hot stretching. Mater Manuf Process, 9(2), 179-197, 1994. 

Pejanovic S, Pavlovic V, Processing of carbon fibers 1, Oxidative stabilization. Extended Abstr Int Carbon Conf Carbone 90, Paris, 152, 16-20 Jul 1990. 

A brief review of microfracture processes and the energy absorption mechanics of fiber reinforced composites is given by Miyajima et al [239]. Fiber pullout is considered to be the most important toughening mechanism. They describe an experimental technique to determine fiber pullout energy, using a 3-point bend specimen. From measurements of fundamental fracture parameters, fracture mechanisms for the fiber pullout processes of carbon fiber reinforced carbon composites are discussed. 

Patankar SN, Gopinathan V, Ramakrishnan P, Processing of carbon fiber reinforced aluminum composite using K2ZrF6 treated carbon fibers, a degradation study, J Mater Sci Lett, 9, 912-913, 1990. 

Figure 4 Flow diagram of the processing of carbon fibers.

D.D.L. Chung, Chapter 2 — processing of carbon fibers, in D.D.L. Chung (Ed.), Carbon Fiber Composites, Butterworth-Heinemann, Boston, 1994, pp. 13—53. 

The application of miaowave irradiation to the processing of carbon fiber-reinforced phenylethynyl-terminated polyimide composites (PETI-5/IM7) was evaluated. A miaowave process was demonstrated that fabricated unidirectional poly-imide-(carbon fiber) composites with superior thermal and mechanical properties relative to the thermal process in half the time required for the thermal process. ... 

Padmavathi, N., Kumari, S., Prasad, V. V. B., Subrahmanyam, J., Ray, K. K. (2009). Processing of carbon-fiber reinforced (SiC + ZrC) mini-composites by soft-solution approach and their characterization. Ceramics International, 35,3447-3454. doi 10.1016/j. ceramint.2009.06.016. 

Scheme 3. Fabrication process of carbon fiber-BN matrix composite.

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