Characterization and control of the fiber-matrix interface in ceramic ...

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126 predicted weight loss was 3%. The flexure results confirmed this suspicion. Only the flexure bars cut from the edge closest to the original cut surface exhibited the expected low strength. The oxidation temperature was kept low to minimize possible matrix damage. This did not allow for the total removal of the carbon layer even though pure oxygen was used to increase the oxidation rate. However, the few specimens did yield useful results. The flexure strengths of the treated and unoxidized specimens are listed in Table 10.1. The oxidized specimens possessed lower matrix fracture strengths and decreased ultimate strength compared with the untreated specimens from the composite sample. Representative flexure curves and photographs of fracture surfaces for oxidized and untreated specimens are shown in Figures 10.16 and 10.17. 10.4.5 Boron coatine; The presence of a boron coating was verified using X-ray line scan data (Figure 10.8). The composite exhibited low flexure strength and little strain-to-failure. This is depicted in the fracture surfaces and the load-displacement curve in Figure 10.18(a). A small degree of fiber pull-out is evident in the SEM photographs, and a closer examination of the fracture surfaces showed the fiber pull-out grooves to be rough and have crystalline appearance (Figure 10.19). A number of fibers also possessed a reaction zone noted by discoloration and an inner boundary line. Thermodynamic evaluation of the coating processes and the stability of the boron in contact with the fibers or matrix predicts that a series of reactions may develop at the interfaces (Table 10.7). Some of these
127 300 I CVI-480 I I 1 0 R N L-DWG 87-1 8236 R 50 0 0 0.0I 0.02 0.03 0.04 0.05 CROSSHEAD DISPLACEMENT (cm) Figure 10.16. Load-displacement curves for specimens containing Nicalon fibers with a carbon intermediate layer: (a) as fabricated and (b) after heating to 1125 K for 44 hours in flowing oxygen.
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ORNL/TM-11039 Metals and Ceramics D
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Page 9.3 Composite Fabrication . .
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LIST OF TABLES Table Page 5,l. Prop
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Figure 8.3. 9.1.. 9.2. 9.3. 9.4. 9.
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Figure 10.18. 10.19. 10.20. 10. 21.
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ACKNOWLEDGMENTS The author wishes t
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CWCTERIZATION AND CONTROL OF THE FI
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1. INTRODUCTION During the last sev
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The development of low-density, hig
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3. FABRICATION TECHNIQUES 3.1 Intro
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11 isostatic pressing (HIP), can be
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13 utilizing the comparatively low-
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16 ORN L- DWG 85- 4 i 4 18RS HEAT1
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5. COMPOSITE DESIGN 5.1 Introductio
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21 5,2 Mechanical Considerations Th
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23 GRNL-DWG 88-74 26 Figure 5.1. Th
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25 Equation (6) shows that the stre
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27 of reinforcement. There are two
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29 in strength. Conversely, the fib
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-I_- Table 5.2. Thermally induced a
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33 1.2 ID 0.8 ;.r 1 e fi v 0.6 a4 Q
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35 will affect the interface and, t
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38 fiber-matrix bonding; thus, a fu
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40 In the analysis of the mechanica
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42 1.2 I .o .6 - E f aa '3 0.6 cn 3
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44 will result in the matrix being
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I I MATRIX MATRIX Figure 7.1. Schem
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48 F = 2a2H, where H is the hardnes
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50 OWL-PHOTO 6866-86 i d c I 20pm F
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52 where Af is the surface area of
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54 Figure 7.4. Tensile and shear st
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56 I I I / -c rc -c / . Om / / I /
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58 ORNL-OWG 87-i 8234 F Figure 7.7.
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coating and the distribution of she
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62 O m PHOTO 6676-87 i SIC FIBERS -
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the composite, therefore an interme
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methane as the reactant and is, thu
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9. EXPERIMENTAL PROCEDURES 9.1 Depo
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71 furnace. The furnace is, therefo
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73 further protection. A 6.5-cm-dia
Page 94 and 95: 76 of the specimen slowly decreased
Page 96 and 97: 78 The programmer is also equipped
Page 98 and 99: 80 graphite holders through multipl
Page 100 and 101: 82 temperature by simply switching
Page 102 and 103: 84 ORNk DWG 87- 4494 3 METAL LOGR A
Page 104 and 105: 86 9.5 Fracture Surface Analvsis Th
Page 106 and 107: 88 treated and untreated halves wer
Page 108 and 109: 90 9.8.2 Tensile testinq In an init
Page 110 and 111: 92 ORNL-DUG 85-11767R.2 ? ! 2 f CEN
Page 112 and 113: 94 fracture of individual Nicalon f
Page 114: 96 Figure 10.1. SiC-infiltrated Nic
Page 117 and 118: 99 compared with the dimensions acq
Page 119 and 120: 101 Table 10.3. Strength and modulu
Page 121 and 122: 100 ORNL- DWG 87-1 6292 R CVI-I73 7
Page 123 and 124: BULK FIBER SAMPLE NO. 173: FIBER SU
Page 125 and 126: 107 similar samples show the film o
Page 127 and 128: Figure 10.7. SEM micrographs showin
Page 129 and 130: 111 Table 10.4. Thermochemical eval
Page 131 and 132: 100 ORNL-DUG 87-15969R CVI- 170 75
Page 133 and 134: 115 Analysis conversion of of the m
Page 135 and 136: 117 A 1 I S N 31 N I I'd I LN 3H 3
Page 137 and 138: 119 n 0 W n 9 v P n w- n v
Page 139 and 140: 121 s m f c I m z - Ir 2 a 0 9 In u
Page 141 and 142: Figure 10.14. SEM micrographs of in
Page 143: J ORNL-DWC 88-6289 z cF u) w I- z O
Page 147 and 148: io0 I I I I CVI- 172 75 - - 0 z v -
Page 149 and 150: 131 RAL 033021 RAL 033023 Figure 10
Page 151: 133 include: the reaction of boron
Page 154 and 155: 136 that BN coatings react with the
Page 156 and 157: 75 7 ORNL-DWG 87-48234 50 - - c5 z
Page 158 and 159: 140 Table 10.9. Thermochemical eval
Page 160 and 161: OANL-bwo 88-9025 ORNL-DWG 66-9027 I
Page 162 and 163: 144 uncoated tows were 14 k 2 pm; t
Page 165 and 166: 11. DISCUSSION 11.1 Constituent Pro
Page 167 and 168: 149 The properties of CVD Sic have
Page 169 and 170: 151 11.2.1 Matrix cracking In the N
Page 171 and 172: 153 OWL-DWG 88-10677 CVI- (78 22 I
Page 173 and 174: 155 Table 11.3. Property comparison
Page 175 and 176: 157 a f ““f f- L c I Figure 11.
Page 177 and 178: 159
Page 179 and 180: 161 The equations demonstrate that
Page 181 and 182: 163 calculations of the matrix depo
Page 183 and 184: 165 In four of the samples, the fib
Page 185 and 186: 167 Table 11.4. Properties of glass
Page 187 and 188: 169 rare-earth magnets and coils to
Page 189 and 190: 171 stress fields along the fiber i
Page 191 and 192: 173 11.3.2 Tensile testinp, The use
Page 193 and 194: 17 5 contraction have been ignored,
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177 the system, and when the result
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180 reduces fiber strength. The str
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182 15. R. A. J. Sambell, D. H. Bow
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184 41. A. J. Caputo et al., "Fiber
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186 71, N. F. DOW, Study of Stresse
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188 98. M. H. Rawlins et al., "Inte
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190 125. R. Warren and C-H. Anderss
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192 155. M. F. Doerner and W, D. Ni
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APPENDIX A. AUGER ELECTRON SPECTROS
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APPENDIX B DETAILS OF THE FIBER-SHE
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200 Those for the fiber (primed) ar
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202 89-92. 93. 94. 95" 96. 97. 98-9
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204 130-133. E. I. DUPONT DE NEMOUR
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206 173. NATIONAL ACADEMY OF SCIENC
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208 203 - 204. 20s. 206 - 207. 208.
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