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Microstructural characteristics affecting crack propagation in carbon-carbon composites
Abstracts
60. Detection of interstitial carbon atoms in a coke during the graphftization J. P. Rouchy and L. Gatineau (C.N.R.S., C.R.S.O.C.I., 45045 Orleans, France). No long or short abstract
submitted.
549
composite fracture. An experimental program was undertaken to observe, at high magnification, crack initiation and propagation mechanisms under tensile loading. These results were used in developing an analytical model for tensile failure based on microstructural parameters and micromechanical principles.
61. Structural evolution of a glassy carbon with the heat treatment between 1000 and 2700°C
and D. Tchoubar (C.N.R.S., Rouneaux C.R.S.O.C.I., 45045 Orleans, France). No long or short abstract submitted. F.
V. MECHANICAL PROPERTIES
62. Dynamic mechanical properties of carbon fibers A. Voet and J. C. Morawski (Centre de Recherches sur la Physico-Chimie des Surfaces Solides-C.N.R.S., Centre Universitaire du Haut-Rhin, 682O@Mulhouse, France). Dynamic mechanical properties in a low
frequency range (O+Ol-10Hz) have been determinid for carbon and graphite fibers at different temperatures. In addition, the influence of fiber stretching has been investigated. Results, showing frequency and extension dependent losses and elastic modulus changes, indicate the presence of large, independently moving fiber constituants, which appear to correspond to the slowly undulating ribbons recognized earlier as carbon fiber components.
66. Microstructure and fracture of graphite J. E. Zimmer and R. A. Meyer (The Aerospace Corporation, Los Angeles, CA 9ooo9). Experimental studies have shown that slow crack propagation in polycrystalline graphite is a direct function of its microstructure. An analytical model that predicts the fracture of graphite based solely on microstructural parameters has been used successfully to identify microstructural process variations that lead to improved graphites. 67. Effect of environment on crack growth in graphite S. W. Freiman and J. J. Mecholsky (Naval Research Laboratory, Washington, D.C. 20375, U.S.A. ). Crack velocities were measured as a function of strain energy release rate for ATJ-S and POCO AXF-SQ graphite in various environments. Little or no effect of external atmosphere on crack propagation was observed at room temperature but atmosphere produced significant changes in behavior at 2300-3000°F.
63. Lightweight glasslike carbon mirrors P. C. Pinoli and W. G. Bradshaw (Lockheed Palo Alto
68. Finite element analysis of an electrode-nipple joint J. M. Faircloth, Jr. (Great Lakes Research Corporation, Research Laboratory, Palo Alto, CA 94304, U.S.A.). Elizabethton, Term, U.S.A.), I. W. Cazda and C. A. The spectral reflectance and angular scattering properties Switzer, Jr. (Great Lakes Carbon Corporation, Niagara of glasslike carbon have been investigated in the range of Fulls, NY, U.S.A.) and 0. T. Sigvaldason and R. G. 0.2- to 25-pm wavelengths. High-quality concave mirrors Charlwood (Acres Consulting Services Limited, Niagara 25.4cm in diameter have been produced, and a Falls, Canada). A solution for the stress-strain distribucopyrolysis-foam substructure has been developed for tion in an electrode-nipple joint is obtained with an support. Physical and mechanical properties of lOOO- axi-symmetric plain constant strain finite element model grade material are compared to those of more convenof two 24”diameter electrodes joined with a nominal 12.5” tional materials. diameter by 14”long threaded and tapered graphite nipple. This mathematical model consists of 4360 triangular 64. Mechanical properties of selected graphites at high elements and has the capability of determining the strain ratest stress-strain distribution in the electrode-nipple joint J. S. Evangelides (The Aerospace Corporation, Los subjected to any combination of axi-symmetrically Angeles, CA, U.S.A.). An experimental program was applied mechanical and thermal loads thus enabling us to conducted to determine the effect of strain rate on flexure study the effects of various joint design modifications and properties and failure mechanisms of graphite. Tests were various combinations of material properties on the conducted at rates of 6 see-’ on graphites with grain sizes stresses and strains in the joint. of 7-400 pm. Flexure strength was strain-rate dependent, and the greatest changes occurred in 7pm graphite. 69. Correlations between the modulus of rupture and the tThis work was supported by the Navy REVMAT program under Air Force Contract No. FO4701-74-C-0075. 65. Microstructural characteristics affecting crack prop-
agation in carbon-carbon compositest J. S. Evangelides (The Aerospace Corporation, Los Angeles, CA, U.S.A.). Microstructural characteristics of
carbon-carbon composites are fundamental in controlling tThis work was supported
by the Navy REVMAT Program
under Air Force Contract No. F04701-74-C-0075.
ultrasonically determined modulus of elasticity in commercial graphites J. M. Faircloth, Jr. (Great Lakes Research Corporation, Elizabethton, Term, U.S.A.) and I. W. Gazda (Great Lakes Carbon Corporation, Niagara Falls, NY, U.S.A.). It is experimentally shown that the moduli of
rupture of artificial graphites correlate well with their moduli of elasticity. This correlation, however, is not the same for all grades of graphite but is found to be influenced by grain size, grain orientation, processing, and raw materials. This relationship of material physical properties becomes of economic and commercial signifi-
60. Detection of interstitial carbon atoms in a coke during the graphftization J. P. Rouchy and L. Gatineau (C.N.R.S., C.R.S.O.C.I., 45045 Orleans, France). No long or short abstract
submitted.
549
composite fracture. An experimental program was undertaken to observe, at high magnification, crack initiation and propagation mechanisms under tensile loading. These results were used in developing an analytical model for tensile failure based on microstructural parameters and micromechanical principles.
61. Structural evolution of a glassy carbon with the heat treatment between 1000 and 2700°C
and D. Tchoubar (C.N.R.S., Rouneaux C.R.S.O.C.I., 45045 Orleans, France). No long or short abstract submitted. F.
V. MECHANICAL PROPERTIES
62. Dynamic mechanical properties of carbon fibers A. Voet and J. C. Morawski (Centre de Recherches sur la Physico-Chimie des Surfaces Solides-C.N.R.S., Centre Universitaire du Haut-Rhin, 682O@Mulhouse, France). Dynamic mechanical properties in a low
frequency range (O+Ol-10Hz) have been determinid for carbon and graphite fibers at different temperatures. In addition, the influence of fiber stretching has been investigated. Results, showing frequency and extension dependent losses and elastic modulus changes, indicate the presence of large, independently moving fiber constituants, which appear to correspond to the slowly undulating ribbons recognized earlier as carbon fiber components.
66. Microstructure and fracture of graphite J. E. Zimmer and R. A. Meyer (The Aerospace Corporation, Los Angeles, CA 9ooo9). Experimental studies have shown that slow crack propagation in polycrystalline graphite is a direct function of its microstructure. An analytical model that predicts the fracture of graphite based solely on microstructural parameters has been used successfully to identify microstructural process variations that lead to improved graphites. 67. Effect of environment on crack growth in graphite S. W. Freiman and J. J. Mecholsky (Naval Research Laboratory, Washington, D.C. 20375, U.S.A. ). Crack velocities were measured as a function of strain energy release rate for ATJ-S and POCO AXF-SQ graphite in various environments. Little or no effect of external atmosphere on crack propagation was observed at room temperature but atmosphere produced significant changes in behavior at 2300-3000°F.
63. Lightweight glasslike carbon mirrors P. C. Pinoli and W. G. Bradshaw (Lockheed Palo Alto
68. Finite element analysis of an electrode-nipple joint J. M. Faircloth, Jr. (Great Lakes Research Corporation, Research Laboratory, Palo Alto, CA 94304, U.S.A.). Elizabethton, Term, U.S.A.), I. W. Cazda and C. A. The spectral reflectance and angular scattering properties Switzer, Jr. (Great Lakes Carbon Corporation, Niagara of glasslike carbon have been investigated in the range of Fulls, NY, U.S.A.) and 0. T. Sigvaldason and R. G. 0.2- to 25-pm wavelengths. High-quality concave mirrors Charlwood (Acres Consulting Services Limited, Niagara 25.4cm in diameter have been produced, and a Falls, Canada). A solution for the stress-strain distribucopyrolysis-foam substructure has been developed for tion in an electrode-nipple joint is obtained with an support. Physical and mechanical properties of lOOO- axi-symmetric plain constant strain finite element model grade material are compared to those of more convenof two 24”diameter electrodes joined with a nominal 12.5” tional materials. diameter by 14”long threaded and tapered graphite nipple. This mathematical model consists of 4360 triangular 64. Mechanical properties of selected graphites at high elements and has the capability of determining the strain ratest stress-strain distribution in the electrode-nipple joint J. S. Evangelides (The Aerospace Corporation, Los subjected to any combination of axi-symmetrically Angeles, CA, U.S.A.). An experimental program was applied mechanical and thermal loads thus enabling us to conducted to determine the effect of strain rate on flexure study the effects of various joint design modifications and properties and failure mechanisms of graphite. Tests were various combinations of material properties on the conducted at rates of 6 see-’ on graphites with grain sizes stresses and strains in the joint. of 7-400 pm. Flexure strength was strain-rate dependent, and the greatest changes occurred in 7pm graphite. 69. Correlations between the modulus of rupture and the tThis work was supported by the Navy REVMAT program under Air Force Contract No. FO4701-74-C-0075. 65. Microstructural characteristics affecting crack prop-
agation in carbon-carbon compositest J. S. Evangelides (The Aerospace Corporation, Los Angeles, CA, U.S.A.). Microstructural characteristics of
carbon-carbon composites are fundamental in controlling tThis work was supported
by the Navy REVMAT Program
under Air Force Contract No. F04701-74-C-0075.
ultrasonically determined modulus of elasticity in commercial graphites J. M. Faircloth, Jr. (Great Lakes Research Corporation, Elizabethton, Term, U.S.A.) and I. W. Gazda (Great Lakes Carbon Corporation, Niagara Falls, NY, U.S.A.). It is experimentally shown that the moduli of
rupture of artificial graphites correlate well with their moduli of elasticity. This correlation, however, is not the same for all grades of graphite but is found to be influenced by grain size, grain orientation, processing, and raw materials. This relationship of material physical properties becomes of economic and commercial signifi-