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Thermal expansion of composites as affected by the matrix
composite as a whole. The implications of these results for fatigue life and fracture behaviour are of great interest. (70/1/81)
Influence of heat treatment on the surface state of quartz fibres Aslanova, M. S., Rudnev, V. S. and Filonenke, A. P. Glass and Ceramics, Vol 26, Nos 7-8, pp 4 0 4 - 406 (July/Aug 1969) The effects of heat treatment between 400°C and 1000°C on the surface state of quartz fibres were studied by electron microscopy. A detailed description is given of the specimen replication technique. It is shown that superficial pre-crystallization microstratification occurs after heat treatment above 400°C, which naturally leads to the development of microcracks and a decrease in the fibre strength. (70/1 [82) Low friction engineering plastics Metallurgia, Vol 81, No 488, p 239 (June 1970) A new PTFE-filled grade of ICI's acetal copolymer, known as Kematal M90-105, has been introduced. The composite combines the low friction properties of Fluon (PTFE) with the versatile processing characteristics of acetal copolymer. It is considered that it will find use as bearings and similar low-friction components. (70/1/83)
Materials testers keep pace with the fibre makers The Engineer, Vol231, No 5977, p 31 (13 A ugust 1970) Some of the methods of fibre property measurement employed at the research laboratories of Fibreglass Ltd of St Helens, Lancashire are briefly described. The problems of gripping fibre specimens in order to examine their stress-strain behaviour on machines such as the Instron tester are pointed out and some of the methods used to overcome them described. (70/1/84) New airframe materials challenge aluminium and steel Graham, R. Design Engineering, pp 36 - 39 (1 September 1970) The efficiency of an aircraft as measured by the ratio of all-up-weight to payload, has been continually increased throughout the history of aircraft manufacture. In a large part, this increase has been made possible by the exploitation of new materials as they have become available. In many cases, the limit of development of conventional airframe materials has been reached and in recent years materials technologists have turned to the lower elements in the
.,390
COMPOSITES December 1970
Periodic Table, which appear to have very desirable properties. Carbon and boron have been successfully used in filamentary form for reinforcement of composites. Some applications of these composites in airframe construction are concluded by the statement: 'The development of composites is, therefore, the logical path to the production of tomorrow's lighter, more efficient and profitable aircraft'. (70/1/85)
New high temperature carbon fibre composite McLoughlin, J. R. Nature, Vol 227, No 5259, p 701 (15 August 1970) Carbon matrix/carbon fibre composites have been prepared which have flexural strengths of 1 2 0 - 1 4 0 x 103 psi at room temperature and 1 2 5 - 1 5 0 x 103 psi at 1500°C (in helium). The type I Morganite fibres are unidirectional and their volume concentration is 7 5 - 8 0 % by weight. The fabrication route consists in impregnation of fibre bundles with resin solutions, evaporation of the solvent, curing under pressure, carbonizing in vacuo at 7 0 0 - 1 0 0 0 ° C , and finally deposition of pyrolytic carbon in the resulting porous structure to densify the matrix. (70/1/86) Production of continuous metal fibres by extrusion from a melt Shepel'ski, N. V. and Zhilkin, V. Z. Soviet Powder Metallurgy, No 10, pp 813 - 817 (September 1969) An apparatus is described for producing metal fibres by extruding the liquid metal through a conical, convergent die. The apparatus was used successfully to extrude fibres of aluminium, copper and lead. The results were used to aid the derivation of equations relating both the rate of solidification o f the emerging jet and the phase transitions in the metal to the rate of extrusion, the geometry of the die, and the physical properties of the metal concerned. (70/1/87) Theoretical estimation of fracture toughness of fibrous composites Piggott, M. R. J Materials Science Vol 5, No 8, pp 669 - 675 (August 1970) A method of estimating fracture surface energy of fibre reinforced materials is discussed. Increasing the fibre content, strength and diameter increased the surface work, and increasing fibre modulus and matrix flow stress decreases the surface work. Relatively short fibres give high toughness and the maximum toughness that can be achieved is limited by the amount of crack opening that can be permitted. Under certain conditions incorporation of fibres into a material can lead to embrittlement. (70/1/88)
Thermal expansion of composites as affected by the matrix Tummala, R. R. and Friedberg, A. L. J American Ceramic Society, Vol 53, No 7, pp 376 - 380 (July 1970) Composites were prepared of particles of silica or zirconia dispersed in matrices of tin, or one of two glasses of different thermal expansion, by the hot pressing of the powdered constituents. The thermal expansions of the composites were measured as a function of volume fraction of the phases. The observed expansion coefficients were predicted by certain theoretical equations provided that internal stresses which result from differences in the thermal expansion of the two phases did not exceed a critical fracture stress. The value of this critical stress was markedly dependent on the ductility of the matrix. (70/1/89) Time-dependent longitudinal strength of unidirectional fibrous composites Lifshitz, J. M. and Rotem, A. Fibre Science and Technology, Vol 3, No 1, p I (July 1970) Theoretical and experimental aspects of the strengths of unidirectional fibre reinforced composites loaded in tension along the fibre axis are reported. Results show that the strength of such materials are time dependent under these loading conditions although due to simplifying assumptions the predicted time to failure is higher than that observed in practice. Both practical and theoretical results indicate that the decrease in strength with time has a lower stress limit below which delayed fracture does not occur. (70[1/90) Variational principles of elastic moduli of composite materials Yeh, R. H. T. J Applied Physics, Vol 41, No 8, pp 3353 - 3356 (July 1970) Variational principles and bounds for the effective elastic moduli of quasiisotropic composite materials are formulated by the method due to Jackson and Coriell. The formulae derived can also be used to describe the viscoelastic behaviour of composites. (70/1/91) Versatile machines w a n t e d - to make components in fibre Mortimer, J. The Engineer, Vol 231, No 5973, p 30 (16July 1970) This general article calls for a great deal o f revised thinking in the development of production techniques and equipment for the manufacture of articles in fibre reinforced materials. A machine which can arrange fibre and resin either into a finished component or into a slug for subsequent machine moulding appears to be one of the primary requirements. (70/1/92)
Influence of heat treatment on the surface state of quartz fibres Aslanova, M. S., Rudnev, V. S. and Filonenke, A. P. Glass and Ceramics, Vol 26, Nos 7-8, pp 4 0 4 - 406 (July/Aug 1969) The effects of heat treatment between 400°C and 1000°C on the surface state of quartz fibres were studied by electron microscopy. A detailed description is given of the specimen replication technique. It is shown that superficial pre-crystallization microstratification occurs after heat treatment above 400°C, which naturally leads to the development of microcracks and a decrease in the fibre strength. (70/1 [82) Low friction engineering plastics Metallurgia, Vol 81, No 488, p 239 (June 1970) A new PTFE-filled grade of ICI's acetal copolymer, known as Kematal M90-105, has been introduced. The composite combines the low friction properties of Fluon (PTFE) with the versatile processing characteristics of acetal copolymer. It is considered that it will find use as bearings and similar low-friction components. (70/1/83)
Materials testers keep pace with the fibre makers The Engineer, Vol231, No 5977, p 31 (13 A ugust 1970) Some of the methods of fibre property measurement employed at the research laboratories of Fibreglass Ltd of St Helens, Lancashire are briefly described. The problems of gripping fibre specimens in order to examine their stress-strain behaviour on machines such as the Instron tester are pointed out and some of the methods used to overcome them described. (70/1/84) New airframe materials challenge aluminium and steel Graham, R. Design Engineering, pp 36 - 39 (1 September 1970) The efficiency of an aircraft as measured by the ratio of all-up-weight to payload, has been continually increased throughout the history of aircraft manufacture. In a large part, this increase has been made possible by the exploitation of new materials as they have become available. In many cases, the limit of development of conventional airframe materials has been reached and in recent years materials technologists have turned to the lower elements in the
.,390
COMPOSITES December 1970
Periodic Table, which appear to have very desirable properties. Carbon and boron have been successfully used in filamentary form for reinforcement of composites. Some applications of these composites in airframe construction are concluded by the statement: 'The development of composites is, therefore, the logical path to the production of tomorrow's lighter, more efficient and profitable aircraft'. (70/1/85)
New high temperature carbon fibre composite McLoughlin, J. R. Nature, Vol 227, No 5259, p 701 (15 August 1970) Carbon matrix/carbon fibre composites have been prepared which have flexural strengths of 1 2 0 - 1 4 0 x 103 psi at room temperature and 1 2 5 - 1 5 0 x 103 psi at 1500°C (in helium). The type I Morganite fibres are unidirectional and their volume concentration is 7 5 - 8 0 % by weight. The fabrication route consists in impregnation of fibre bundles with resin solutions, evaporation of the solvent, curing under pressure, carbonizing in vacuo at 7 0 0 - 1 0 0 0 ° C , and finally deposition of pyrolytic carbon in the resulting porous structure to densify the matrix. (70/1/86) Production of continuous metal fibres by extrusion from a melt Shepel'ski, N. V. and Zhilkin, V. Z. Soviet Powder Metallurgy, No 10, pp 813 - 817 (September 1969) An apparatus is described for producing metal fibres by extruding the liquid metal through a conical, convergent die. The apparatus was used successfully to extrude fibres of aluminium, copper and lead. The results were used to aid the derivation of equations relating both the rate of solidification o f the emerging jet and the phase transitions in the metal to the rate of extrusion, the geometry of the die, and the physical properties of the metal concerned. (70/1/87) Theoretical estimation of fracture toughness of fibrous composites Piggott, M. R. J Materials Science Vol 5, No 8, pp 669 - 675 (August 1970) A method of estimating fracture surface energy of fibre reinforced materials is discussed. Increasing the fibre content, strength and diameter increased the surface work, and increasing fibre modulus and matrix flow stress decreases the surface work. Relatively short fibres give high toughness and the maximum toughness that can be achieved is limited by the amount of crack opening that can be permitted. Under certain conditions incorporation of fibres into a material can lead to embrittlement. (70/1/88)
Thermal expansion of composites as affected by the matrix Tummala, R. R. and Friedberg, A. L. J American Ceramic Society, Vol 53, No 7, pp 376 - 380 (July 1970) Composites were prepared of particles of silica or zirconia dispersed in matrices of tin, or one of two glasses of different thermal expansion, by the hot pressing of the powdered constituents. The thermal expansions of the composites were measured as a function of volume fraction of the phases. The observed expansion coefficients were predicted by certain theoretical equations provided that internal stresses which result from differences in the thermal expansion of the two phases did not exceed a critical fracture stress. The value of this critical stress was markedly dependent on the ductility of the matrix. (70/1/89) Time-dependent longitudinal strength of unidirectional fibrous composites Lifshitz, J. M. and Rotem, A. Fibre Science and Technology, Vol 3, No 1, p I (July 1970) Theoretical and experimental aspects of the strengths of unidirectional fibre reinforced composites loaded in tension along the fibre axis are reported. Results show that the strength of such materials are time dependent under these loading conditions although due to simplifying assumptions the predicted time to failure is higher than that observed in practice. Both practical and theoretical results indicate that the decrease in strength with time has a lower stress limit below which delayed fracture does not occur. (70[1/90) Variational principles of elastic moduli of composite materials Yeh, R. H. T. J Applied Physics, Vol 41, No 8, pp 3353 - 3356 (July 1970) Variational principles and bounds for the effective elastic moduli of quasiisotropic composite materials are formulated by the method due to Jackson and Coriell. The formulae derived can also be used to describe the viscoelastic behaviour of composites. (70/1/91) Versatile machines w a n t e d - to make components in fibre Mortimer, J. The Engineer, Vol 231, No 5973, p 30 (16July 1970) This general article calls for a great deal o f revised thinking in the development of production techniques and equipment for the manufacture of articles in fibre reinforced materials. A machine which can arrange fibre and resin either into a finished component or into a slug for subsequent machine moulding appears to be one of the primary requirements. (70/1/92)