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

More documents

Recommendations

Info

Strengthening with fibers has so many advantages-- high strength, toughness, high-temperature strength, thermal. stability, and cheap, light and chemically inactive materials for the fibers -- that it seems certain to become the basis of engineering solids of the future. The main problems are technological. We have to develop ways of making and assembling the fibers cheaply by the ton and develop new methods of engineering design and fabrication to make best use of their properties. These developments will require great effore but the stakes are high. A. H. Cottrell (1) xvi
CWCTERIZATION AND CONTROL OF THE FIBER-MATRIX INTERFACE IN CERAMIC MATRIX COMPOSITE? R. A. Lowden ABSTRACT Fiber-reinforced Sic composites fabricated by thermal-gradient forced-flow chemical-vapor infiltration (FCVI) have exhibited both composite (toughened) and brittle behavior during meehanlcal property evaluation. Detailed analysis of the fiber-matrix interface revealed that a silica layer on the surface of Nicalon Si-C-0 fibers ti.ghtly bonds the fiber to the matrix. The strongly bonded fiber and matrix, combined wi.th the reduction in the strength of the fibers that occurs during processing, resulted in the observed brittle behavior. The mechanical behavior of Nical.on/SiC composites has been improved by applying thin coatings to the fibers, prior to densification, to control the interfacial bond. Varying degrees of bonding have been achieved with different coating materials and film thicknesses. Fiber-matrix bond strengths have been quantitatively evaluated using an indentation method and a simple tensile test. The effects of bonding and friction on the mechanical behavior of this composite system have been investigated. Fiber coatings not only weaken the fiber-matrix bond, increasing toughness, but can protect the fibers from chemical attack and hinder *Research sponsored by the U. S . Department of Energy, AR&TD Fossil Energy Materials Program [DOE/FE AA 15 10 10 0, Work Breakdown Structure Element ORNL-l(c)] under contract DE-AC05-840K21400 with Martin Marietta Energy Systems, Inc, 1
Page 3: ORNL/TM-11039 Metals and Ceramics D
Page 6 and 7: Page 9.3 Composite Fabrication . .
Page 9: LIST OF TABLES Table Page 5,l. Prop
Page 12 and 13: Figure 8.3. 9.1.. 9.2. 9.3. 9.4. 9.
Page 14 and 15: Figure 10.18. 10.19. 10.20. 10. 21.
Page 17: ACKNOWLEDGMENTS The author wishes t
Page 21: 1. INTRODUCTION During the last sev
Page 24 and 25: The development of low-density, hig
Page 27 and 28: 3. FABRICATION TECHNIQUES 3.1 Intro
Page 29 and 30: 11 isostatic pressing (HIP), can be
Page 31: 13 utilizing the comparatively low-
Page 34 and 35: 16 ORN L- DWG 85- 4 i 4 18RS HEAT1
Page 37 and 38: 5. COMPOSITE DESIGN 5.1 Introductio
Page 39 and 40: 21 5,2 Mechanical Considerations Th
Page 41 and 42: 23 GRNL-DWG 88-74 26 Figure 5.1. Th
Page 43 and 44: 25 Equation (6) shows that the stre
Page 45 and 46: 27 of reinforcement. There are two
Page 47 and 48: 29 in strength. Conversely, the fib
Page 49 and 50: -I_- Table 5.2. Thermally induced a
Page 51 and 52: 33 1.2 ID 0.8 ;.r 1 e fi v 0.6 a4 Q
Page 53: 35 will affect the interface and, t
Page 56 and 57: 38 fiber-matrix bonding; thus, a fu
Page 58 and 59: 40 In the analysis of the mechanica
Page 60 and 61: 42 1.2 I .o .6 - E f aa '3 0.6 cn 3
Page 62 and 63: 44 will result in the matrix being
Page 64 and 65: I I MATRIX MATRIX Figure 7.1. Schem
Page 66 and 67: 48 F = 2a2H, where H is the hardnes
Page 68 and 69:
50 OWL-PHOTO 6866-86 i d c I 20pm F
Page 70 and 71:
52 where Af is the surface area of
Page 72 and 73:
54 Figure 7.4. Tensile and shear st
Page 74 and 75:
56 I I I / -c rc -c / . Om / / I /
Page 76 and 77:
58 ORNL-OWG 87-i 8234 F Figure 7.7.
Page 78 and 79:
coating and the distribution of she
Page 80 and 81:
62 O m PHOTO 6676-87 i SIC FIBERS -
Page 83 and 84:
the composite, therefore an interme
Page 85 and 86:
methane as the reactant and is, thu
Page 87 and 88:
9. EXPERIMENTAL PROCEDURES 9.1 Depo
Page 89 and 90:
71 furnace. The furnace is, therefo
Page 91 and 92:
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 and 144:
J ORNL-DWC 88-6289 z cF u) w I- z O
Page 145 and 146:
127 300 I CVI-480 I I 1 0 R N L-DWG
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,
Page 195:
177 the system, and when the result
Page 198 and 199:
180 reduces fiber strength. The str
Page 200 and 201:
182 15. R. A. J. Sambell, D. H. Bow
Page 202 and 203:
184 41. A. J. Caputo et al., "Fiber
Page 204 and 205:
186 71, N. F. DOW, Study of Stresse
Page 206 and 207:
188 98. M. H. Rawlins et al., "Inte
Page 208 and 209:
190 125. R. Warren and C-H. Anderss
Page 210 and 211:
192 155. M. F. Doerner and W, D. Ni
Page 213 and 214:
APPENDIX A. AUGER ELECTRON SPECTROS
Page 215:
APPENDIX B DETAILS OF THE FIBER-SHE
Page 218 and 219:
200 Those for the fiber (primed) ar
Page 220 and 221:
202 89-92. 93. 94. 95" 96. 97. 98-9
Page 222 and 223:
204 130-133. E. I. DUPONT DE NEMOUR
Page 224 and 225:
206 173. NATIONAL ACADEMY OF SCIENC
Page 226 and 227:
208 203 - 204. 20s. 206 - 207. 208.
show all

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

Create successful ePaper yourself

Delete template?

Save as template?