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Discussion of ‘A theory for the mechanical properties of metal matrix composites at ultimate loading’
dicular and parallel to the lameUar orientation. It was found that the rate of diffusion of zinc into a-A1 plateletsis greater than expected for lattice diffusion. The diffusion of zinc into the 0-CuA12 platelets causes their transformation into a structure of mparticles in a matrix of ~'-A13ZnCu3. The process is slower in the platelets than it is in bulk CuA13 and this is attributed to lateral diffusion of zinc into the adjacent a platelets. The results indicate the a-r boundaries act as high-diffusivity paths. Discussion of "A theory for the mechanical properties of metal matrix composites at ultimate loading' Avitzuer, B. Metallurgical Transactions,
Vo14, No 10 (Oct 1973}pp 2478-2480 The theory presented in the earlier paper by Garmong and Thomson
(Met Trans, Vol 4 (1973) pp 863-873) is discussed and a number o f weaknesses in the theory are suggested. It is concluded that the theory should only be considered as an approximation method. The discussion is followed by a reply from the authors.
occurred after long-term exposure. This is attributed to dissolution of oxygen in the nickel and subsequent internal oxidation of the tungsten that is dissolved in the nickel. A model for the reaction mechanism is proposed.
Strength properties of high-porosity metal fibre materials Kostorn.or, A. G., Shevchuk, M. S. and Gorb, M. L. Soviet Powder
Metallurgy and Metal Ceramics, Vo111, No 4 (Apr 1972)pp 326-329 Fibrous composites of the alloy 20% Cr-80% Ni with various pore fractions were produced by pressing and sintering 50 #m diameter fibres of chromium and nickel. The tensile strengths of the composites were determined as a function of porosity and temperature. It was found that the strength did not fall as sharply with porosity as it does in conventional powder materials. The composite with 40% porosity retained a relatively high strength ( 3 - 4 kg/mm z) up to 1100°C. Such composites have possible applications as high-temperature materials that can be internally cooled.
Fibre reinforcement of metals (in Swedish) Lowenalder, L. G. Kemisk Tidskrift, Vol 85, No 12 (Dec 1973)pp 52-57 A comprehensive review is made of the current state of development of fibre-reinforced, metal-matrix composites. The possible techniques of composite fabrication and factors of importance in the preparation and applications of such composites are discussed with reference to known composite systems. The future development and potential of metal matrix composites is discussed.
High-temperature stability of Ni/W-fibre composites in oxygen atmospheres Kvernes, I. and Kofstad, P.
Scandinavian Journal of Metallurgy, Vol 2, No 6 (Dec 1973) pp 291-297 The oxidation at temperatures between 800 ° and 1200°C of composites of nickel reinforced with 22 volume % tungsten wires was investigated. Catastrophic degradation of the composites occurred when the tungsten fibre ends were exposed directly to the oxygen atmosphere. The oxidation resistance was improved considerably when the exposed tungsten was covered by coating the entire composite with nickel. Even so, degradation of the composite
188
RESIN MA TRICES
Acrylic backed composite structures Editorial Plastics Technology, Vol 19, No 12 (Nov 1973)pp 42-43 In order to prevent the surface defects which typicall arise in grp gel coats a thin sheet of acrylic is first formed in the mould, thus forming an acrylic surface with a high degree of perfection. Normal spray up techniques for grp, tilled or unfilled as required, are employed to build up the structural layers of the component. A number of mechanical and aesthetic advantages are achieved by this type of construction.
Bulk f'dlers can do more than decrease polyester cost Gibilisco, R. A. Plastics Design and Processing, Vol 13, No 9 (Sep 1973) pp 10-11 The influence of bulk fillers on the viscosity, gel time and peak exotherm of a polyester resin catalyzed with cumene peroxide and accelerated with cobalt octoate was studied. Viscosity changes ranging from a few per cent
to several hundred per cent were obtained with 48% tiller. Gel times varied from 14 to 160 rain and peak exotherm temperatures from 65.6 ° to 118°C (150 ° to 245°F) Composites formed by interstitial polymerization of vinyl monomers in polyurethane dastomer: 1. Preparation and mechanical properties of methyl
methacrylate based composites .Mien, G. et al Polymer, Vo114, No 12 (Dec 1973) pp 597-603 The physical and mechanical properties of cast sheets of PMMA in PU gel were found to depend on the initiator concentration, molar ratio of isocyanates to hydroxyl groups, time between gelation and polymerization of the MMA, the crosslink density of the PU and the ratio of PMMA to PU. Optimum impact strengths of 12.5 kJ/m 2 (for notched impact) and shear modul of 0.65 GN/m 2 were obtained, compared to 1.2 kJ/m 2 for PMMA homopolymer.
Composites formed by interstitial polymerization of vinyl monomers in polyurethane elastomer: 2. Morphology and relaxation processes in methyl methacrylate based composites Allen, G. et al Polymer, Vo114, No 12 (Dec 1973) pp 604-616 The structure of PMMA/PU composites formed by interstitial polymerization was observed to consist of PMMA domains embedded in a PU matrix. There is, however, some interaction between the polymeric species. An attempt was made to correlate the variations in domain size and molecular motion with the mechanical properties of the composite.
Expensive composites save money (in Swedish) Bernsten, U. and Kleivan, A. Teknish Tidskrift, Vol 103, No 11 (15Jun 1973)pp 11-14 A brief description is given of carbon and boron fibre reinforced plastics. The properties of these composites are reviewed and compared with those of metallic materials, particularly with regard to cost. Their potential applications are discussed and current examples of their use are given. Proposed tests of reinforced plastic components in aircraft, to be carried out by the aircraft division of Saab-Scania are briefly described.
COMPOSITES. JULY 1974
Vo14, No 10 (Oct 1973}pp 2478-2480 The theory presented in the earlier paper by Garmong and Thomson
(Met Trans, Vol 4 (1973) pp 863-873) is discussed and a number o f weaknesses in the theory are suggested. It is concluded that the theory should only be considered as an approximation method. The discussion is followed by a reply from the authors.
occurred after long-term exposure. This is attributed to dissolution of oxygen in the nickel and subsequent internal oxidation of the tungsten that is dissolved in the nickel. A model for the reaction mechanism is proposed.
Strength properties of high-porosity metal fibre materials Kostorn.or, A. G., Shevchuk, M. S. and Gorb, M. L. Soviet Powder
Metallurgy and Metal Ceramics, Vo111, No 4 (Apr 1972)pp 326-329 Fibrous composites of the alloy 20% Cr-80% Ni with various pore fractions were produced by pressing and sintering 50 #m diameter fibres of chromium and nickel. The tensile strengths of the composites were determined as a function of porosity and temperature. It was found that the strength did not fall as sharply with porosity as it does in conventional powder materials. The composite with 40% porosity retained a relatively high strength ( 3 - 4 kg/mm z) up to 1100°C. Such composites have possible applications as high-temperature materials that can be internally cooled.
Fibre reinforcement of metals (in Swedish) Lowenalder, L. G. Kemisk Tidskrift, Vol 85, No 12 (Dec 1973)pp 52-57 A comprehensive review is made of the current state of development of fibre-reinforced, metal-matrix composites. The possible techniques of composite fabrication and factors of importance in the preparation and applications of such composites are discussed with reference to known composite systems. The future development and potential of metal matrix composites is discussed.
High-temperature stability of Ni/W-fibre composites in oxygen atmospheres Kvernes, I. and Kofstad, P.
Scandinavian Journal of Metallurgy, Vol 2, No 6 (Dec 1973) pp 291-297 The oxidation at temperatures between 800 ° and 1200°C of composites of nickel reinforced with 22 volume % tungsten wires was investigated. Catastrophic degradation of the composites occurred when the tungsten fibre ends were exposed directly to the oxygen atmosphere. The oxidation resistance was improved considerably when the exposed tungsten was covered by coating the entire composite with nickel. Even so, degradation of the composite
188
RESIN MA TRICES
Acrylic backed composite structures Editorial Plastics Technology, Vol 19, No 12 (Nov 1973)pp 42-43 In order to prevent the surface defects which typicall arise in grp gel coats a thin sheet of acrylic is first formed in the mould, thus forming an acrylic surface with a high degree of perfection. Normal spray up techniques for grp, tilled or unfilled as required, are employed to build up the structural layers of the component. A number of mechanical and aesthetic advantages are achieved by this type of construction.
Bulk f'dlers can do more than decrease polyester cost Gibilisco, R. A. Plastics Design and Processing, Vol 13, No 9 (Sep 1973) pp 10-11 The influence of bulk fillers on the viscosity, gel time and peak exotherm of a polyester resin catalyzed with cumene peroxide and accelerated with cobalt octoate was studied. Viscosity changes ranging from a few per cent
to several hundred per cent were obtained with 48% tiller. Gel times varied from 14 to 160 rain and peak exotherm temperatures from 65.6 ° to 118°C (150 ° to 245°F) Composites formed by interstitial polymerization of vinyl monomers in polyurethane dastomer: 1. Preparation and mechanical properties of methyl
methacrylate based composites .Mien, G. et al Polymer, Vo114, No 12 (Dec 1973) pp 597-603 The physical and mechanical properties of cast sheets of PMMA in PU gel were found to depend on the initiator concentration, molar ratio of isocyanates to hydroxyl groups, time between gelation and polymerization of the MMA, the crosslink density of the PU and the ratio of PMMA to PU. Optimum impact strengths of 12.5 kJ/m 2 (for notched impact) and shear modul of 0.65 GN/m 2 were obtained, compared to 1.2 kJ/m 2 for PMMA homopolymer.
Composites formed by interstitial polymerization of vinyl monomers in polyurethane elastomer: 2. Morphology and relaxation processes in methyl methacrylate based composites Allen, G. et al Polymer, Vo114, No 12 (Dec 1973) pp 604-616 The structure of PMMA/PU composites formed by interstitial polymerization was observed to consist of PMMA domains embedded in a PU matrix. There is, however, some interaction between the polymeric species. An attempt was made to correlate the variations in domain size and molecular motion with the mechanical properties of the composite.
Expensive composites save money (in Swedish) Bernsten, U. and Kleivan, A. Teknish Tidskrift, Vol 103, No 11 (15Jun 1973)pp 11-14 A brief description is given of carbon and boron fibre reinforced plastics. The properties of these composites are reviewed and compared with those of metallic materials, particularly with regard to cost. Their potential applications are discussed and current examples of their use are given. Proposed tests of reinforced plastic components in aircraft, to be carried out by the aircraft division of Saab-Scania are briefly described.
COMPOSITES. JULY 1974