Developments in Ceramic Materials Research

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204 M. A. Sheik These are also signs of less sudden changes in flow direction at the crossover locations which forces flux concentration there as well although to a less degree than the shape change phenomenon mentioned above. This behavior has been expected within such a crimp weave composite cloth and shows a thermal behavior that could be expected of a woven composite. Although this behavior may be slightly reduced with the help of certain effort in smoothing the remaining sharp cuts on the lofted regions during the modelling process but its positive impact is expected to be minimal and therefore not a worthwhile exercise. Figure 35 ‘In-plane’ Steady-State heat flux in X-direction (arrow) for the complete HITCO RVE Unit Cell with flow contours seen (a) in an in-plane slice across XZ-plane, (b) across thickness in YZ-plane, heat flowing normal to the page, (c and d) across thickness in XY-plane, (e) in fibre tows only (without matrix). Figure 36. ‘Through-thickness’ Steady-State heat flux in Y-direction (arrow) for the complete HITCO RVE Unit Cell with flow contours seen (a) with in-plane slice across XZ-plane, (b) across thickness in YZ-plane, heat flowing normal to the page, (c and d) across thickness in XY-plane, (e) in fibre tows only (without matrix).
Modeling of Thermal Transport in Ceramics Matrix Composites 205 The heat flux concentration is 25% greater than the in-plane heat flux (light green) indicating that sudden change in flow direction has been dictated by fibre tow undulations and this is how the heat is expected to flow through the composite fabric across the dominant heat flow x-direction. An overall flow contour summary is given in Figure 32 and Figure 33 for inplane and through-thickness heat flow scenarios respectively for the full composite RVE Unit Cell (except in Figures 32(e) and 33(e) where matrix is removed). The arrows depict the prevailing heat flux direction in each case. It is imperative that the final results obtained bare similarity to the experimental data and this has been shown in Table 8 with limited input information for the FE analysis as far as constituent material properties are concerned. The input values taken for the modified matrix region was calculated from Equation 14 using rule of mixtures as the matrix and air in voids and cracks, comprising the bulk porosity, do have isotropic thermal conductivity. Hence an input value of k = 18.72 has been used based on the values of k and k mp m p given in Table 9. Table 8. Values of Thermal Conductivity of the Constituent Materials Material k (W m -1 K -1 ) Volume Fraction (%) Carbon Fibre Transverse 7 50 Carbon Fibre Longitudinal 70 Carbon Matrix 28 39 Air (porosity) 0.001 11 Table 9. FE analyses compared with Manufacturer’s Thermal Conductivity Data (W.m -1 K -1 ) Experimental Data Numerical Analysis (Steady-State) In-plane 28 25.656 (+ 8%) Through-Thickness 8 9.79 (- 22%) 5. COMPUTATIONAL ASPECTS It has been highlighted earlier that with the increase in the geometric complexity of the CMCs, the requirement of the computing resources has risen. This has been reiterated by the current modelling effort with 8-harness satin weave geometry, apart from the modelling challenge of the HITCO materials’ fibre tow weave pattern which alone has been massive enough. It can be reckoned that with the multiplication of the Unit Cell (each containing around a Million elements) across the lamina and then the laminate, demand for computational power increases drastically. Special arrangement is therefore required for conducting analysis of such large FE models. Earlier DLR-XT Unit Cell had been managed within a single-CPU desktop machine operating on Windows XP with 80 Gigabytes storage space and 512 Megabytes physical memory. It has also been observed how the machine had been swapping its hard disk for need of fast storage; as much as 1.8 Gigabytes at times, almost 4 times the physical memory. In that case, the element count had not exceeded 200,000 whereas in the present case this figure
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DEVELOPMENTS IN CERAMIC MATERIALS R
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Copyright © 2007 by Nova Science P
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PREFACE Ceramics are refractory, in
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Preface ix crystals is discussed. A
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Preface xi spectra and the directio
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2 Leslie G. Cecil comprehensive dat
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4 Leslie G. Cecil Ringle et al. (19
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6 Leslie G. Cecil The main architec
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8 Leslie G. Cecil can study “the
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10 Leslie G. Cecil Middleton et al.
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12 Leslie G. Cecil The laser ablate
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14 Leslie G. Cecil There are two ge
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16 Leslie G. Cecil distinct recipes
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18 Leslie G. Cecil second group (Fi
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20 Leslie G. Cecil The Vitzil-Orang
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22 Leslie G. Cecil Table 3. Mahalan
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24 Leslie G. Cecil Ixlú and Ch’i
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26 Leslie G. Cecil structures (D. R
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28 Leslie G. Cecil paste and Macanc
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30 Leslie G. Cecil Bieber, A. M. Jr
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32 Leslie G. Cecil Kepecs, S. M., a
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34 Leslie G. Cecil Schele, L., Grub
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36 Z. C. Li, Z. J. Pei and C. Tread
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54 T. T. Basiev, V. A. Demidenko, K
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62 I, % 100 80 60 40 20 0 T. T. Bas
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68 Fluorescence, a.u. 1 T. T. Basie
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70 Fluorescence, a.u. 1 0.1 0.01 0.
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78 k, cm -1 20 18 16 14 12 10 8 6 4
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82 Photon counts 300 250 200 150 10
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84 Fluorescence, a.u. I transfer ,
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86 ln(I transfer (t)) -4.2 -4.4 -4.
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88 Fluorescence, a.u. I transfer ,
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In: Developments in Ceramic Materia
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Synthesis, Spectroscopic and Magnet
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a c Synthesis, Spectroscopic and Ma
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Transmission Transmission Transmiss
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Sm (J/Kmol) Sm (J/Kmol) 15 10 5 Syn
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Intensity (a.u.) Intensity (a.u.) 8
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In: Developments in Ceramic Materia
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The Use of Ceramic Pots in Old Wors
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3.2. Wall-in Positions The Use of C
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Page 260 and 261: 246 Li Chen The continuing evolutio
Page 262 and 263: 248 Li Chen the back contact cathod
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254 Li Chen Figure 8(a). I-V curve
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256 Li Chen Figure 9. Life time tes
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258 Figure 11(a). Plasma generated
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260 Li Chen [13] C.A. Spindt, K.R.
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262 S. Ardizzone, C. L. Bianchi, G.
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A absorption spectra, 66, 67, 77, 7
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correlation function, 156 corrosion
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group membership, 13, 20, 21, 22, 2
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microstructure(s), x, xi, 73, 74, 2
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efraction index, 61 refractive inde
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time, vii, ix, 1, 3, 7, 8, 11, 26,
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Developments in Ceramic Materials Research

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