Carbon fiber Thermal conductivity

Fig. 8. Comparison of electrical and thermal conductivity of PAN- and pitch-based carbon fiber to metals, where P = pitch, T = Thornel, and...

Because of their unique blend of properties, composites reinforced with high performance carbon fibers find use in many structural applications. However, it is possible to produce carbon fibers with very different properties, depending on the precursor used and processing conditions employed. Commercially, continuous high performance carbon fibers currently are formed from two precursor fibers, polyacrylonitrile (PAN) and mesophase pitch. The PAN-based carbon fiber dominates the ultra-high strength, high temperature fiber market (and represents about 90% of the total carbon fiber production), while the mesophase pitch fibers can achieve stiffnesses and thermal conductivities unsurpassed by any other continuous fiber. This chapter compares the processes, structures, and properties of these two classes of fibers. 

In contrast, there is also current interest in investigating PAN-based fibers in low thermal conductivity composites [62], Such fibers are carbonized at low temperature and offer a substitute to rayon-based carbon fibers in composites designed for solid rocket motor nozzles and exit cones. 

Edie, D. D., Robinson, K. E., Fleurot, O., Jones, S. P. and Fain, C. C., High thermal conductivity ribbon fibers from naphthalene-based mesophase. Carbon, 1994, 32(6), 1045 1054. 

Applied Sciences, Inc. has, in the past few years, used the fixed catalyst fiber to fabricate and analyze VGCF-reinforced composites which could be candidate materials for thermal management substrates in high density, high power electronic devices and space power system radiator fins and high performance applications such as plasma facing components in experimental nuclear fusion reactors. These composites include carbon/carbon (CC) composites, polymer matrix composites, and metal matrix composites (MMC). Measurements have been made of thermal conductivity, coefficient of thermal expansion (CTE), tensile strength, and tensile modulus. Representative results are described below. 

Duffy, D.R., Ting, J.-M., Guth, J.R. and Lake, M.L., Carbon fiber reinforced lightweight composites with ultra high thermal conductivities, Proc. Int. JEPC, Atlanta, GA, Sept., 1994, pp. 442 448. 

Ting, J.M. and Lake, M.L., Vapor grown carbon fiber reinforced aluminum composites with very high thermal conductivity J. Mat. Res., 1995, 10(2), 247 250. 

Fig. 18. The temperature dependence of the thermal conductivity of hybrid carbon fiber monoliths measured in the to fibers direction at two densities.

Dinwiddie, R.B., Nelson, G.E., and Weaver, C.E., The effect of sub-minute high temperature heat treatments on the thermal conductivity of carbon-bonded carbon fiber (CBCF) insulation. In Proc. Thermal Conductivity 23, ed. K.E. Wilkes, R.B. Dinwiddie and R.S. Graves, Technomic Pub. Co., Inc., Lancaster, PA, 1996, pp. 466 477. 

Because direct calculation of thermal conductivity is difficulty 1], experimental measurements on composites with nanotubes aligned in the matrix could be a first step for addressing the thermal conductivity of carbon nanotubes. High on-axis thermal conductivities for CCVD high-temperature treated carbon fibers have been obtained, but have not reached the in-plane thermal conductivity of graphite (ref. [3], Fig. 5.11, p. 115). We expect that the radial thermal conductivity in MWNTs will be very low, perhaps even lower than the c-axis thermal conductivity of graphite. 

---