Carbon fibers structure models

The structure from the core to the surface of the fiber varies also. A model for the PAN-based carbon fiber structure proposed by Diefendorf and reported by Drzal [29]... 

Affected by multiple scattering are, in particular, porous materials with high electron density (e.g., graphite, carbon fibers). The multiple scattering of isotropic two-phase materials is treated by Luzatti [81] based on the Fourier transform theory. Perret and Ruland [31,82] generalize his theory and describe how to quantify the effect. For the simple structural model of Debye and Bueche [17], Ruland and Tompa [83] compute the effect of the inevitable multiple scattering on determined structural parameters of the studied material. 

Fiber spinning, 11 174, 175, 170-171 carbon-nanotube, 13 385-386 methods of, 16 8 models of, 11 171-172 of polyester fibers, 20 12-15 Fiber structure, of aromatic polyamides, 19 727... 

Heat conductivity of composite materials are severely and adversely affected by structural defects in the material. These defects are due to voids, uneven distribution of filler, agglomerates of some materials, unwetted particles, etc. Figure 15.18 shows the effect of filler concentration on thermal conductivity of polyethylene. Graphite, which is a heat conductive material, increases conductivity at a substantially lower concentration than does quartz. These data agree with the theoretical predictions of model. Figure 15.19 shows the effect of volume content and aspect ratio of carbon fiber on thermal conductivity. This figure should be compared with Figure 15.17 to see that, unlike electric conductivity which does depend on the aspect ratio of the carbon fiber, the thermal conductivity is only dependent on fiber concentration and increases as it increases. 

Studies on MWCNT electronic properties have shown that they behave like an ultimate carbon fiber [77] at high temperature their electrical conductivity can be described by the semiclassical models already used for graphite, while at low temperature they reveal two-dimensional quantum transport features. A reliable prediction of their electronic properties is even more difficult than in the case of SWCNTs, due to the higher complexity of their structure, and experimental measurements on MWCNT resistivity have not given reliable values (Table 9.2), due to different CNT purities and measuring conditions. 

Observers look for an upturned in late 2004 or 2005 of carbon reinforced composites. Boeing and Airbus are using more carbon fiber on their new models, and older models take on more carbon as they get updated. Innovative aerospace fabricators push the carbon-fiber envelope with new, low-cost advanced RPs such as pultruded key parts on the Airbus A380. The huge Airbus A380 will carry 30 metric tons/66,000 lb of structural composites 16% of its airfirame weight. 

Figure 32 shows the schematic structure of the tested CFRP sample. The CFRP sample had a multilayered structure of CFRP cloth. The carbon fibers in one layer of cloth were aligned unidirectionally and the adjacent layers of cloth were set cross-directionally. The thickness of CFRP cloth was 70 pm, and the examined CFRP sample was composed of 72 layers of doth (about 5 mm thickness in all). In order to model the separation of the CFRP layers (defect), a Teflon sheet (80 pm in thickness) was sandwiched between the 54th and the 55th layers of CFRP cloth, at a level 3.8 mm below the CFRP top surface. The sound velocity and the acoustic impedance of the CFRP sample are about 3 X 10 m/s and 5 x 10 Pa s/m, respectively. Water was used as the coupling medium because of its low ultrasonic attenuation characteristics, and the CFRP... 

Figure 5.20 Proposed three dimensional structural model of HM carbon fiber depicting interlinked crystallinity.

Diefendorf and Tokarski [78] subscribe to the view of a wrinkled ribbon of carbon fiber with modulus about 275 GPa, where the ribbons are about 13 layers thick, 4nm wide and at least a few microns long. For fibers with a modulus of about 750 GPa, the ribbons are about 30 layers thick and 9 nm wide, with almost zero amplitude and essentially parallel to the fiber axis. Figure 5.28 gives a three dimensional view of the ribbon structure with a model shown in Figure 5.29. 

Figure 5.21 A probable three dimensional structural model for a PAN based HM carbon fiber. Source Reprinted with permission from Barnett FR, Norr MK, Proceedings of the International Conference on Carbon Fibres, their Composites and Applications, London (Plastics Institute), 32, 1974. Copyright 1974, Maney Publishing (who administers the copyright on behalf of lOM Communications Ltd., a wholly owned subsidiary of the Institute of Materials, Minerals Mining).

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