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Role of load and the oxidising gas during preoxidation of PAN on the properties of carbon fibers
Abstracts
555
118. Heat treatment bebaviour of carbon fibre-carbon predictions from current theories of composite fracture. Pull-out and surface formation appear to be the major composites energy absorbing processes. L. Boyne, J. Hill and K. Turner (AWRE, MOD(PE), Aldermaston, Berks, U.K.). This paper shows that the 123. The modulus and strength of carbon fibers strength of carbon fibre glossy carbon composites E. W. Tokarsky (Hercules Inc., Research Center, increases with heat treatment over the range 1500-2500°C Wilmington, DE, U.S.A.) and R. J. Diefendorf (Renwhen pyrocarbon densiftcation has been used, but only sselaer Polytechnic Institute, Materials Engineering Defor surface treated fibres. Untreated fibre composites, which can be considerably stronger in the densified state, partment, Troy, NY 12181, U.S.A.). No short abstract submitted. tend to have their strength reduced by heat treatment. 119. The influence of copolymer content of the PAN precursor and of tensile load during oxidation and carbonization on the formation of carbon fibres E. Fitzer and J. Simitzis (Institut fur Chemische Technik, Uniuersitat Karlsruhe, W. Germany). In situ measurement of length changes during isothermal oxidation and during the carbonization heating are performed with PAN fibres of varied metbylacrylat copolymer contents up to 5%. The effect of precursor composition and of polymer fibre fabrication conditions as well as of textile pre-stretching on the chemical reactions during carbon fibre formation and on the final carbon fibre properties are discussed in detail. 120. Compression fracture and microhardness cbaracteristies of carbon fibres H. M. Hawthorne and E. Teghtsoonian (Centre for Materials Research, University of British Columbia, Vancouver, Canada). Fracture of moderately oriented
pitch-, PAN- and rayon-based carbon fibres is similar in axial compression and elastica loop bending tests. Failure initiates preferentially in fibre outer layers by a buckling of the more ordered and aligned, but less interconnected, microfibrils thus accounting for the non-Hookean elastic bending behaviour and the diminished axial compression strength observed in most such fibres. Microhardness of carbon fibres also depends on the degree of lateral coupling existing between microfibrils. 121. Pyrolyzed composites from chopped fibers in highchar yield polymeric precursors W. G. Bradsbaw and P. C. Pinoli (Lockheed Palo Alto Research
Laboratory,
122. Fracture energy of carbon-carbon and carbon-resin composites E. J. Walker and J. Hill (Ministry of Defence (PE) Aldermaston, Berks, England). Work of fracture was measured by slow bend and Cbarpy impact methods on carbon-carbon and carbon-resin composites. Fair agreement was found between the observed data and
13 NO. 64
technic Institute, Materials Engineering Dept., Troy, NY 12181, U.S.A.). No short abstract submitted.
125. Role of load and the oxidiiing gas during preoxidation of PAN on the propertiesof carbon fibers 0. P. Bahl and L. M. Manocha (Carbon Technology Unit, National Physical Laboratory, New Delhi-l 10012, India). Air has been found to be a better oxidising agent
than oxygen. Effect of load in both these gases has been studied in detail. Two broad stages of elongation have been observed in the presence of oxygen while in the presence of air elongation takes place only in one stage. Mechanical properties have been found to improve with elongation in the first stage while the tensile strength falls down in the second stage in the presence of oxygen. Implications are discussed. 126. Heterogeneitiesin carbon fibers D. R. Uhlmann and S. B. Warner (Department of Materials Science and Engineering, Massachusetts tute of Technology, Cambridge, MA, U.S.A.) and Peebles, Jr. (Office of Naval Research, Boston, U.S.A.). Acrylic, stabilized acrylic, and graphite
Insti-
L. H. MA,
fibers have been examined on the electron microscope following ion bombardment. Structures traversing the fiber are observed and interpreted on the basis of heterogeneities, suggesting that the heterogeneous nature of the graphite fiber arises from heterogeneities in the precursor fiber and their development during subsequent processing.
Palo Alto, CA 94304, U.S.A.).
Preliminary studies have been conducted to demonstrate the feasibility of producing high-density carbon-carbon composites with good mechanical properties using high-char yielding graphitizable resins to minimize the number of processing steps. Without impregnation, composites with moderately high density, low porosity, and good mechanical properties can be obtained.
CAR VOL.
124. Effects of fiber strength and surface treatmenton the fractures of graphite/epoxycomposites J. W. Nelson (Corning Glass Works, Coming, NY 14830, U.S.A.) and R. J. Diefendorf (Renesselaer Poly-
127 and 128. High modulus carbon fibersfrom mesophase pitcbt R. Didchenko, J. B. Barr, S. Chwastiak, I. C. Lewis, R. T. Lewis and L. S. Singer (Union Carbide Corporation, Parma Technical Center, Cleveland, OH 44101, U.S.A.). (Parts 1 and 2). Highly oriented carbon fibers have been
produced without stretching from mesophase pitches.3 Phase composition, molecular weight distribution, and flow properties of these pitches have been studied. Fibers spun from the mesophase pitches have a high degree of longitudinal orientation and exhibit several types of radial orientation. The highest tensile strength achieved so far tWork partially supported by AFML, Wright-Patterson Air Force Base, Ohio. $Singer L. S., Be/g. Pat. 797,543(1973).
555
118. Heat treatment bebaviour of carbon fibre-carbon predictions from current theories of composite fracture. Pull-out and surface formation appear to be the major composites energy absorbing processes. L. Boyne, J. Hill and K. Turner (AWRE, MOD(PE), Aldermaston, Berks, U.K.). This paper shows that the 123. The modulus and strength of carbon fibers strength of carbon fibre glossy carbon composites E. W. Tokarsky (Hercules Inc., Research Center, increases with heat treatment over the range 1500-2500°C Wilmington, DE, U.S.A.) and R. J. Diefendorf (Renwhen pyrocarbon densiftcation has been used, but only sselaer Polytechnic Institute, Materials Engineering Defor surface treated fibres. Untreated fibre composites, which can be considerably stronger in the densified state, partment, Troy, NY 12181, U.S.A.). No short abstract submitted. tend to have their strength reduced by heat treatment. 119. The influence of copolymer content of the PAN precursor and of tensile load during oxidation and carbonization on the formation of carbon fibres E. Fitzer and J. Simitzis (Institut fur Chemische Technik, Uniuersitat Karlsruhe, W. Germany). In situ measurement of length changes during isothermal oxidation and during the carbonization heating are performed with PAN fibres of varied metbylacrylat copolymer contents up to 5%. The effect of precursor composition and of polymer fibre fabrication conditions as well as of textile pre-stretching on the chemical reactions during carbon fibre formation and on the final carbon fibre properties are discussed in detail. 120. Compression fracture and microhardness cbaracteristies of carbon fibres H. M. Hawthorne and E. Teghtsoonian (Centre for Materials Research, University of British Columbia, Vancouver, Canada). Fracture of moderately oriented
pitch-, PAN- and rayon-based carbon fibres is similar in axial compression and elastica loop bending tests. Failure initiates preferentially in fibre outer layers by a buckling of the more ordered and aligned, but less interconnected, microfibrils thus accounting for the non-Hookean elastic bending behaviour and the diminished axial compression strength observed in most such fibres. Microhardness of carbon fibres also depends on the degree of lateral coupling existing between microfibrils. 121. Pyrolyzed composites from chopped fibers in highchar yield polymeric precursors W. G. Bradsbaw and P. C. Pinoli (Lockheed Palo Alto Research
Laboratory,
122. Fracture energy of carbon-carbon and carbon-resin composites E. J. Walker and J. Hill (Ministry of Defence (PE) Aldermaston, Berks, England). Work of fracture was measured by slow bend and Cbarpy impact methods on carbon-carbon and carbon-resin composites. Fair agreement was found between the observed data and
13 NO. 64
technic Institute, Materials Engineering Dept., Troy, NY 12181, U.S.A.). No short abstract submitted.
125. Role of load and the oxidiiing gas during preoxidation of PAN on the propertiesof carbon fibers 0. P. Bahl and L. M. Manocha (Carbon Technology Unit, National Physical Laboratory, New Delhi-l 10012, India). Air has been found to be a better oxidising agent
than oxygen. Effect of load in both these gases has been studied in detail. Two broad stages of elongation have been observed in the presence of oxygen while in the presence of air elongation takes place only in one stage. Mechanical properties have been found to improve with elongation in the first stage while the tensile strength falls down in the second stage in the presence of oxygen. Implications are discussed. 126. Heterogeneitiesin carbon fibers D. R. Uhlmann and S. B. Warner (Department of Materials Science and Engineering, Massachusetts tute of Technology, Cambridge, MA, U.S.A.) and Peebles, Jr. (Office of Naval Research, Boston, U.S.A.). Acrylic, stabilized acrylic, and graphite
Insti-
L. H. MA,
fibers have been examined on the electron microscope following ion bombardment. Structures traversing the fiber are observed and interpreted on the basis of heterogeneities, suggesting that the heterogeneous nature of the graphite fiber arises from heterogeneities in the precursor fiber and their development during subsequent processing.
Palo Alto, CA 94304, U.S.A.).
Preliminary studies have been conducted to demonstrate the feasibility of producing high-density carbon-carbon composites with good mechanical properties using high-char yielding graphitizable resins to minimize the number of processing steps. Without impregnation, composites with moderately high density, low porosity, and good mechanical properties can be obtained.
CAR VOL.
124. Effects of fiber strength and surface treatmenton the fractures of graphite/epoxycomposites J. W. Nelson (Corning Glass Works, Coming, NY 14830, U.S.A.) and R. J. Diefendorf (Renesselaer Poly-
127 and 128. High modulus carbon fibersfrom mesophase pitcbt R. Didchenko, J. B. Barr, S. Chwastiak, I. C. Lewis, R. T. Lewis and L. S. Singer (Union Carbide Corporation, Parma Technical Center, Cleveland, OH 44101, U.S.A.). (Parts 1 and 2). Highly oriented carbon fibers have been
produced without stretching from mesophase pitches.3 Phase composition, molecular weight distribution, and flow properties of these pitches have been studied. Fibers spun from the mesophase pitches have a high degree of longitudinal orientation and exhibit several types of radial orientation. The highest tensile strength achieved so far tWork partially supported by AFML, Wright-Patterson Air Force Base, Ohio. $Singer L. S., Be/g. Pat. 797,543(1973).