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Pyrolytic carbon infiltration of fibrous structures
332
ABSTRACTS
31. Pyrolytic carbon infiltration of fibrous structures J. J. Gebhardt (Re-entry and Environmental Systems Division, General Electric Company, Philadelphia, Pennsylvania). Experimentally derived empirical correlations will be presented which describe the influence of deposition parameters on the pyrolytic infiltration of woven and other fibrous carbon constructions of varying densities and geometries. Results are interpreted in terms of the influence of the above factors on gas phase reaction and diffusion rates within the porous structure. 32. Effect of variation in precursor resin on the properties of PHS carbon composites W. Bradshaw (Lockheed Missiles and Space Co., Palo Alto, California). Alteration of the matrix precursor resin can be used to cause significant changes in the degree of graphitization, crystallite size and basal plane of orientation of the pyrolysed matrix in PHS carbon composites. Such changes in matrix morphology were utilized to obtain substantial improvement in the impulse threshold under dynamic loading. With respect to static mechanical properties, the most significant improvement was an increase in the amount of plastic strain-to-failure. 33. Fabrication and CVD carbon infiltration of carbon and graphite filament wound cylinders D. W. Bauer, W. V. Kotlensky, J. W. Warren and W. H. Smith (Super-Temp Company Santa Fe Springs, California) and Early Gray (Thiokol Chemical Corporation, Brigham City, Utah). Carbon and graphite yarns were dry wound on eleven 2 in. i.d. X 2.4 in. o.d. X 12 in. long graphite mandrels using a nominal 75” helical wind angle. The yarns were produced from three different precursors rayon, PAN and pitch. Variables investigated included yarn denier, ply, carbon and graphite states and high modulus graphite yarns and tow. Density for the as-wound cylinders varied from 0.51 g/cm3 to 0.92 g/cm3. Cylinders were infiltrated to densities as high as 1.77 g/cm. Cylinders were also graphitized and coated with CVD carbon to seal the surface and to determine the compatibility of fiber with coatings. The relation between yarn characteristics and the infiltration behavior of the filament wound structures will be discussed. 34. CVD Carbon infiltration and strength for fabric lay-up carbon/carbon composites D. W. Bauer and W. V. Kotlensky (Super-Temp Company, Santa Fe SP_ings, California). Fabric lay-up structures were studied to determine the effect of fabric type, weave, and fiber volume on infiltration and strength. Six different fabrics were investigated: (1) HITCO G-1550 8 H/S graphite cloth; (2) HITCO SS-1808 open weave carbon cloth; (3) Carborundum GSCC-8, 8 H/S carbon cloth; (4) Kureha l/l square weave carbon cloth; (5) Kureha 2 A 2 square weave carbon cloth and (6) Kureha 8 H/S carbon cloth. The open weave SS-1808 carbon cloth were found to have a marked effect on the infiltration behavior. Infiltrated densities as high as 1.8 g/cm3 were achieved. Flexural, compressive, shear and impact measurements were made to characterize the strength. The most sensitive measurement with processing and structure was the shear strength. Shear strength values up to 6000 psi were measured. 35. Carbon-carbon composites fabricated by wet winding endless carbon fibers with pitch E. Fitzer and B. Terwiesch (Institute fur Chemische Technik der Uniuersitat Karlsruhe, West Germany). A study was performed on unidirectional fiber reinforced composites using gas pressure during the baking process. Data on physical and mechanical properties are presented and discussed in comparison with results on carbon-carbon composites using resin binders. Such composites can be used as model for the discussion of the interaction between filler and binder in carbon artifacts. 36. Pyrostrand graphite composite E. L. Olcott (Atlantic Research Corporation, Shirley Highway at E&all Rd., Alexandria, Virginia). Pyrostrand graphite composite was recently developed at Atlantic Research to take advantage of the desirable properties of pyrolytic graphite and at the same time, to reduce the anisotropy and thereby make a material more suited to structural applications. The Pyrostrand graphite composite contains only pyrolytic graphite deposited at a temperature of 3800°F and a graphite filament reinforcement. There are some disconnected pores, estimated to be approximately 3 per cent, which exist between the graphite filament turns. A dense pyrolytic graphite layer between each yarn layer also contributes to the impermeable nature of the structure, The pyrolytic graphite is formed by passing methane over a heated releasable substrate which also supports the positioned graphite filaments. Deposition conditions are 3800°F temperature and 26 in. of mercury vacuum. The nature of the composite can be varied by the use of different graphite filament reinforcements and in different quantities. Higher fiber content
ABSTRACTS
31. Pyrolytic carbon infiltration of fibrous structures J. J. Gebhardt (Re-entry and Environmental Systems Division, General Electric Company, Philadelphia, Pennsylvania). Experimentally derived empirical correlations will be presented which describe the influence of deposition parameters on the pyrolytic infiltration of woven and other fibrous carbon constructions of varying densities and geometries. Results are interpreted in terms of the influence of the above factors on gas phase reaction and diffusion rates within the porous structure. 32. Effect of variation in precursor resin on the properties of PHS carbon composites W. Bradshaw (Lockheed Missiles and Space Co., Palo Alto, California). Alteration of the matrix precursor resin can be used to cause significant changes in the degree of graphitization, crystallite size and basal plane of orientation of the pyrolysed matrix in PHS carbon composites. Such changes in matrix morphology were utilized to obtain substantial improvement in the impulse threshold under dynamic loading. With respect to static mechanical properties, the most significant improvement was an increase in the amount of plastic strain-to-failure. 33. Fabrication and CVD carbon infiltration of carbon and graphite filament wound cylinders D. W. Bauer, W. V. Kotlensky, J. W. Warren and W. H. Smith (Super-Temp Company Santa Fe Springs, California) and Early Gray (Thiokol Chemical Corporation, Brigham City, Utah). Carbon and graphite yarns were dry wound on eleven 2 in. i.d. X 2.4 in. o.d. X 12 in. long graphite mandrels using a nominal 75” helical wind angle. The yarns were produced from three different precursors rayon, PAN and pitch. Variables investigated included yarn denier, ply, carbon and graphite states and high modulus graphite yarns and tow. Density for the as-wound cylinders varied from 0.51 g/cm3 to 0.92 g/cm3. Cylinders were infiltrated to densities as high as 1.77 g/cm. Cylinders were also graphitized and coated with CVD carbon to seal the surface and to determine the compatibility of fiber with coatings. The relation between yarn characteristics and the infiltration behavior of the filament wound structures will be discussed. 34. CVD Carbon infiltration and strength for fabric lay-up carbon/carbon composites D. W. Bauer and W. V. Kotlensky (Super-Temp Company, Santa Fe SP_ings, California). Fabric lay-up structures were studied to determine the effect of fabric type, weave, and fiber volume on infiltration and strength. Six different fabrics were investigated: (1) HITCO G-1550 8 H/S graphite cloth; (2) HITCO SS-1808 open weave carbon cloth; (3) Carborundum GSCC-8, 8 H/S carbon cloth; (4) Kureha l/l square weave carbon cloth; (5) Kureha 2 A 2 square weave carbon cloth and (6) Kureha 8 H/S carbon cloth. The open weave SS-1808 carbon cloth were found to have a marked effect on the infiltration behavior. Infiltrated densities as high as 1.8 g/cm3 were achieved. Flexural, compressive, shear and impact measurements were made to characterize the strength. The most sensitive measurement with processing and structure was the shear strength. Shear strength values up to 6000 psi were measured. 35. Carbon-carbon composites fabricated by wet winding endless carbon fibers with pitch E. Fitzer and B. Terwiesch (Institute fur Chemische Technik der Uniuersitat Karlsruhe, West Germany). A study was performed on unidirectional fiber reinforced composites using gas pressure during the baking process. Data on physical and mechanical properties are presented and discussed in comparison with results on carbon-carbon composites using resin binders. Such composites can be used as model for the discussion of the interaction between filler and binder in carbon artifacts. 36. Pyrostrand graphite composite E. L. Olcott (Atlantic Research Corporation, Shirley Highway at E&all Rd., Alexandria, Virginia). Pyrostrand graphite composite was recently developed at Atlantic Research to take advantage of the desirable properties of pyrolytic graphite and at the same time, to reduce the anisotropy and thereby make a material more suited to structural applications. The Pyrostrand graphite composite contains only pyrolytic graphite deposited at a temperature of 3800°F and a graphite filament reinforcement. There are some disconnected pores, estimated to be approximately 3 per cent, which exist between the graphite filament turns. A dense pyrolytic graphite layer between each yarn layer also contributes to the impermeable nature of the structure, The pyrolytic graphite is formed by passing methane over a heated releasable substrate which also supports the positioned graphite filaments. Deposition conditions are 3800°F temperature and 26 in. of mercury vacuum. The nature of the composite can be varied by the use of different graphite filament reinforcements and in different quantities. Higher fiber content