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PEEK laminates using acoustic emission
Migration of particles during extrusion of metal matrix composites Ehrstrom, J. C. and Kool, W. H. Journal o f Materials Science Letters Vol 7 (1988) pp 578-580 Metal matrix composites consisting of SiC particles reinforcing a AISiTMg5 alloy matrix were fabricated using three different routes: addition of SiC by stirring into the semi-solid alloy followed by either casting or meltspinning and by mixing the alloy powder and SiC particles. All routes were followed by extrusion. Except for the conventionally cast billet, extrusion was found to affect the distribution of SiC particles under some circumstances. Possible explanations are given.
RESIN MA TRICES Controlled interfacial bonding on the residual strength of fatigued-damaged carbon fibreepoxy composites Yiu-Wing Mai Journal o f Materials Science Letters Vol 7 (1988) pp 581-582 The effect of coating carbon fibres with polyurethane varnish or silicone vacuum oil on the residual strength of carbon fibre reinforced epoxy laminates subjected to fatigue loading is reported. A monotonic increase in residual strength with number of cycles was found for the polyurethane coated fibres, whilst the residual strength of the silicone oil coated fibres showed a peak. Explanations for this behaviour are presented. Debonding and friction at fibre.polymer interfaces. H. Macroscopic model experiments Piggott, M. R. and Dai, S. R. Composites Science and Technology Vo131 No I (1988) pp 15-24 Experiments devised to determine whether the curved plot of debonding force vs embedded length was an artefact of the pull-out test or whether it provided evidence of an actual interface failure mechanism in a fibre-composite material are described. Steel drill rods were embedded in cured epoxy resin inside steel or plastic tubes and pulled out using an Instron servo-hydraulic machine. A wide range of embedded lengths was tested. It appeared from the pull-out tests that debonding is a brittle fracture process at all embedded lengths. Dynamic delamination fracture toughness of a graphite/epoxy laminate under impact Sun, C. T. and Grady, J. E. Composites Science and Technology Vol 31 No 1 (1988) pp 55-72 Dynamic delamination fracture toughness in a [90]5, T300/934 graphite/epoxy laminate was investigated using impact loading. Delamination cracks of three different sizes were embedded at the mid-plane of the specimen. The threshold impact velocity that causes propagation of the delamination crack was used in the dynamic analysis with the finite element method. Compared with values of static fracture toughness, the dynamic values are shown to be much higher. It is pointed out, though, that the crack tip sharpness which is infinite in mathematical models was blunt in the experiment.
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Electrical conduction phenomena between adjacent stainless steel fibres in a thermoplastic matrix Bridge, B., Folkes, M. J. and Jahankhani, H. Journal o f Materials Science Vo123 No 6 (1988) pp 1955-1960 A model system consisting of two, nontouching, stainless steel wires embedded in a polypropylene matrix is used to study the mechanisms involved in the conduction process in reinforced thermoplastics. The gap between one end of a wire and the other was about 100 microns. It was found that a homogeneous conduction model does not explain the observed resistances. Fractography of unfilled and particulatefilled epoxy resins Cantwell, W. J., Roulin-Moloney, A. C. and Kaiser, T. Journal o f Materials Science Vol 23 No 5 (1988) pp 1615-1631 The effects of the thermo-mechanical history on the fracture surface morphology of an unfilled and a silica-filled epoxy resin are studied. Short-term tensile tests and longterm creep tests were carried out at four temperatures. The effect of crack velocity on fracture surface morphology was also studied. The morphology of failed surfaces is related to the mechanisms of fracture. The influence of fibre stocking sequence on the high vdocity impact response of CFRP Cantwell, W. J. Journal o f Materials Science Letters Vol 7 No 7 (1988) pp 756-758 The effect of stacking sequence on the high velocity impact resistance of XAS 914C carbon fibre epoxy laminates is reported. Damage was assessed using C-scan. Mixed woven composites were found to possess the best impact resistance, however they also had the lowest resistance to perforation. Damage increased with the number of ply interfaces present. The in-plane shear modulus of fibre reinforced composites as defined by the concept of interphase Sideridis, E. Composites Science and Technology Vo131 No I (1988) pp 35-53 A model is presented, based on classical elasticity theory, of a composite unit cell which consists of three phases: the fibre, the matrix and the interphase (described as that part of the polymer matrix, lying close to the fibre, which possesses different physicochemical properties from those of the main constituents). The thickness of the interphase was determined by thermal analysis. The model was compared with experimental data for the in-plane shear modulus of a material comprising an epoxy matrix reinforced with long E-glass fibres and was found to more nearly represent experimental values than other theories. A micrographic study of bending failure in five thermoplastic-carbon fibre composite laminates Yurgatis, S. W. and Sternstein, S. S. Journal o f Materials Science Vol 23 No 5 (1988) pp 1861-1870 The bending failure of five thermoplastic composites (polycarbonate, polysulphone, polyphenylenesulphide, polyethersulphone and polyetheretherketone, all with carbonfibre reinforcement) were observed under a microscope. The laminate lay-up was (0/90)2 s and the span to thickness ratio was about
39:1. Their behaviour is compared to that of an epoxy carbon-fibre laminate. It was concluded that the thermoplastic comlx~itcs were superior to epoxy composites in suppressing delamination failure in bending. However, the thermoplastic composites were more prone to longitudinal compression failure. Relation between work of fracture and fracture toughness of short fibre-reinfeceed polymers Lauke, B. and Pompe, W. Composites Science and Technology Vol 31 No 1 (1988~ p p 25-33 Mathematical expressions are derived for w, the work of fracture, and G¢, fracture toughness, for short fibre-reinforced polymers by first determining the crack-resistance curve. It is shown that both parameters are necessary to describe failure behaviour; Gc for crack instability, or strength; and w as the energy necessary to drive the crack through the sample. In many cases, the work of fracture was found to be much higher than the fracture toughness. Simulation of the percolation threshold in metal fibre loaded conductive bridge polymer composites Bridge, B. Journal o f Materials Science Letters Vol 7 No 6 (1988) pp 663-665 In order to overcome the difficulties in the calculation of the perculation threshold (the volume fraction of conducting fibres in a non-conducting matrix at which conductivity increases rapidly), the author has constructed a model of the electrical behaviour of such a composite. It was found that the model's behaviour agreed well with resistivity measurements in a real material. A study of the development of impact damage in cross-ply carbon fibre/PEEK laminates using acoustic emission Nixon, J. A., Phillips, M. G., Moore, D. R. and Prediger, R. S. Composites Science and Technology Vo131 No I (1988) pp 1-14 Instrumented falling weight impact tests were performed on [0/90h0s APC-2/AS4 laminates to investigate damage development. It was observed that at an input energy of 4.9 J the onset of delamination occurred. The specimens were afterwards subjected to four-point bending tests with acoustic emission (AE) monitoring and the critical level of impact energy was seen to be associated with a sharp change in the evolution of AE under increasing load. The AE behaviour was shown to be different for laminates with and without delamination, indicating that A E may be used for the detection of sub-critical damage and, with further development, the rest may be made semi-quantitative. Surface pretreatment and adhesion of ti~rmoplastic fibre-composites Kodokian, G. K. A. and Kinloch, A. J. Journal o f Materials Science Letters Vol 7 No 6 (1988) pp 625-627 The effects of surface pretreatment on the fracture toughness of adhesively bonded APC-2 (carbon fibre/PEEK) and 913C XAS (carbon-fibre/epoxy) are reported. The surface pretreatments were: abrasion, moulding, next to aluminium foil (to reduce release agent pick-up), acid etch and corona dis-, charge. Rubber-toughened epoxy and PEEK were used in adhesives. For all surface
COMPOSITES. JANUARY 1989)
treatments in the case of the APC-2 material, it was found that epoxy gave poor bond strengths. It is suggested that this is due to the poor bond strengths. It is suggested that this is due to the poor wettability and intrinsic adhesion of the PEEKmaterial. Use of Weibull statistics to quantify specimen size effects in fatigue of GRP Crowther, M. F. and Starkey, M. S.
Composites Science and Technology Vol 31 No 2 (1988) pp 87-95 Data are presented to show that changing specimen size has considerable effect on the fatigue life of unidirectional GRP. Weibull statistics are used in an attempt to quantify the change in fatigue life that would be expected from size effects alone and the predictions tested against experimental data obtained for unidirectional glass fibre-
reinforced epoxy composites tested in flexure. It is shown that, where material and processing variables are kept constant, the model predicts the change in fatigue life with stressed volume with reasonable accuracy. It is stated that the model will also allow the effect attributable to change in dimensions of a specimen to be separated from the effects attributable to a change in material properties.
Abstracts of British Patents are prepared by Dr F. R. Jones, Department of Ceramics, Glasses and Polymers, University of Sheffield, UK
UK PATENTS COMPONENTS Bonding thermoplastic materials (The Welding Institute, UK) GB 2 200 590 A (10 August 1988) iCarbon fibre thermoplastic prepreg is used as the adhesive interlayer for a fusion weld whereby the fibres act as the heating element. I i
!Joining earl~n-c~rbon materials (Acurex Corp, USA) GB 2 201 122.4 (24 August 1988) A carhonisable interlayer such as pitch is used to stabilise a compression joint between two carbon fibre reinforced carbon materials.
GB 2 201 117 A (24 August 1988) A polyurethane foam is used as an in situ mandrel or for filling FRP layed-up onto an inflatable mandrel. The manufacture of lightweight extruded structural profile (M, J. Hewitt, UK) GB 2 202 180 A/GB 2 202 182 A (21 September 1988) A technique for continuous pultrusion of a graded particulate filled GRP sheath is described whereby the fillers are vacuum compacted sequentially with the finer fillers filling the interstices between the coarse filler particles. The particles are normally foamed to give a lightweight profile.
US PATENTS COMPONENTS
WA TERIALS CremJi~able polyphenylene oxide resin commtttm Matsushita Electric Works Ltd, Japan) ~B 2 200 128 A (27 July 1988) The described matrix has applications for :omposite laminates as printed circuit board mbstrates, with enhanced heat and chemical resistance. Polyimtde-siloxanes method of making and General Electric Company, USA) GB 2 200 647 A (10 August 1988) These condensation polymers have applications in semiconductor devices and composites. Heat insulating laminates (Man Technologic GmbH, FRG) GB 2 201 373 A (1 September 1988) Ceramic material for use at 1000°C and above is made from reflective layers consisthag of a subtrate of impregnated, fired ceramic fibres and a noble metal interdispersed with alumina fibrous wadding.
PROCESSES ~ n g process for composite hockey stidm (Charing Inn Aluminium Industry Co Ltd, Talwan)
COMPOSITES. JANUARY 1989
Composite thread line sails Conrad, P. G. (Sobstad Sailmakers Incorporated, Old Saybrook, CT, USA) US Pat 4 708 080 (24 November 1987) A sail, with a head, a tack, and a clew, which in use has principal stress lines is made up from a number of joined panels. Each panel is a laminate consisiting of at least two layers between which is non-woven, force-bearing thread material predeterminedly disposed along the lines of stress. Club-head Kobayashi, M. (Maruman Company Limited, Tokyo, Japan) US Pat 4 708 347 (24 November 1987) A golf club head made from a number of separate portions is described. The main body, made from fibre-reinforced plastic, contains a weight of heavy material and is attached to a metal sole. Extruder die for extrusion of a thermoplastic laminate Reifenhfiuser, H., Reitemeyer, P., Krumm, K. and Beisemann, H. (Reifenhauser GmbH and Company Maschinenfabrik, Troisdorf, FRG) US Pat 4 708 618 (24 November 1987) A die for the extrusion of a multilayer thermoplastic laminate in the form of a foil or plate is described. Environmentally protected electrical contact terminal arrangement for a plastic-metalplastic laminated cycle fender
Belka, H. (ESGE-Marby GmbH and Company KG, Bielefeld, FRG) US Pat 4 708 665 (24 November 1987) The cycle fender comprises two layers of plastic within which is embedded a layer of metal foil. Within the fender is a shaft filled with ribbed rivet-shaped metal, the head of which rests upon the upper plastic layer and the body of which contains and provides electrical contact with the metal foil. Method of making a flexible bearing McGregor, J. D. (Morton Thiokol Incorporated, Chicago, IL, USA) US Pat 4 708 757 (24 November 1987) The bearing comprises first and second rigid end rings with flexible laminations between; the laminations consisting of alternating layers of elastomeric material and rigid reinforcement shims made of fabric material impregnated with resin. The whole bearing shape conforms to surfaces of concentric spheres. The bearing is made by first pressing and compacting each uncured resin impregnated fabric reinforceinent into the required shape. The bearing is then assembled in a mould and subjected to heat and pressure to cure the reinforcement and vulcanize the elastomeric material.
MATERIALS Zirconium metal matrix-silicon carbide coin. posite nuclear reactor components Ferrari, H, M. (Westinghouse Electric Corporation, Pittsburgh, PA, USA) US Pat 4 707 330 (17 November 1987) Metallic components, including fuel cladding, control rods, rod guide thimbles, grids and channels, of a nuclear reactor are made from a metal matrix composite comprising 90-60 vol% Zr or a zirconium alloy (containing <5% alloying element) reinforced with 10-40 vol% SiC whiskers. Bicomponent ceramic fibres Rambosek, G. M. (Minnesota Mining and Manufacturing Company, St Paul, MN, USA) US Pat 4 707 399 (17 November 1987) A continuous, bicomponent, non-vitreous ceramic fibre, circular, oval or rod-like in cross-section comprises two ceramic components extending longitudinally side-by-side, each component being derived from a
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RESIN MA TRICES Controlled interfacial bonding on the residual strength of fatigued-damaged carbon fibreepoxy composites Yiu-Wing Mai Journal o f Materials Science Letters Vol 7 (1988) pp 581-582 The effect of coating carbon fibres with polyurethane varnish or silicone vacuum oil on the residual strength of carbon fibre reinforced epoxy laminates subjected to fatigue loading is reported. A monotonic increase in residual strength with number of cycles was found for the polyurethane coated fibres, whilst the residual strength of the silicone oil coated fibres showed a peak. Explanations for this behaviour are presented. Debonding and friction at fibre.polymer interfaces. H. Macroscopic model experiments Piggott, M. R. and Dai, S. R. Composites Science and Technology Vo131 No I (1988) pp 15-24 Experiments devised to determine whether the curved plot of debonding force vs embedded length was an artefact of the pull-out test or whether it provided evidence of an actual interface failure mechanism in a fibre-composite material are described. Steel drill rods were embedded in cured epoxy resin inside steel or plastic tubes and pulled out using an Instron servo-hydraulic machine. A wide range of embedded lengths was tested. It appeared from the pull-out tests that debonding is a brittle fracture process at all embedded lengths. Dynamic delamination fracture toughness of a graphite/epoxy laminate under impact Sun, C. T. and Grady, J. E. Composites Science and Technology Vol 31 No 1 (1988) pp 55-72 Dynamic delamination fracture toughness in a [90]5, T300/934 graphite/epoxy laminate was investigated using impact loading. Delamination cracks of three different sizes were embedded at the mid-plane of the specimen. The threshold impact velocity that causes propagation of the delamination crack was used in the dynamic analysis with the finite element method. Compared with values of static fracture toughness, the dynamic values are shown to be much higher. It is pointed out, though, that the crack tip sharpness which is infinite in mathematical models was blunt in the experiment.
94
Electrical conduction phenomena between adjacent stainless steel fibres in a thermoplastic matrix Bridge, B., Folkes, M. J. and Jahankhani, H. Journal o f Materials Science Vo123 No 6 (1988) pp 1955-1960 A model system consisting of two, nontouching, stainless steel wires embedded in a polypropylene matrix is used to study the mechanisms involved in the conduction process in reinforced thermoplastics. The gap between one end of a wire and the other was about 100 microns. It was found that a homogeneous conduction model does not explain the observed resistances. Fractography of unfilled and particulatefilled epoxy resins Cantwell, W. J., Roulin-Moloney, A. C. and Kaiser, T. Journal o f Materials Science Vol 23 No 5 (1988) pp 1615-1631 The effects of the thermo-mechanical history on the fracture surface morphology of an unfilled and a silica-filled epoxy resin are studied. Short-term tensile tests and longterm creep tests were carried out at four temperatures. The effect of crack velocity on fracture surface morphology was also studied. The morphology of failed surfaces is related to the mechanisms of fracture. The influence of fibre stocking sequence on the high vdocity impact response of CFRP Cantwell, W. J. Journal o f Materials Science Letters Vol 7 No 7 (1988) pp 756-758 The effect of stacking sequence on the high velocity impact resistance of XAS 914C carbon fibre epoxy laminates is reported. Damage was assessed using C-scan. Mixed woven composites were found to possess the best impact resistance, however they also had the lowest resistance to perforation. Damage increased with the number of ply interfaces present. The in-plane shear modulus of fibre reinforced composites as defined by the concept of interphase Sideridis, E. Composites Science and Technology Vo131 No I (1988) pp 35-53 A model is presented, based on classical elasticity theory, of a composite unit cell which consists of three phases: the fibre, the matrix and the interphase (described as that part of the polymer matrix, lying close to the fibre, which possesses different physicochemical properties from those of the main constituents). The thickness of the interphase was determined by thermal analysis. The model was compared with experimental data for the in-plane shear modulus of a material comprising an epoxy matrix reinforced with long E-glass fibres and was found to more nearly represent experimental values than other theories. A micrographic study of bending failure in five thermoplastic-carbon fibre composite laminates Yurgatis, S. W. and Sternstein, S. S. Journal o f Materials Science Vol 23 No 5 (1988) pp 1861-1870 The bending failure of five thermoplastic composites (polycarbonate, polysulphone, polyphenylenesulphide, polyethersulphone and polyetheretherketone, all with carbonfibre reinforcement) were observed under a microscope. The laminate lay-up was (0/90)2 s and the span to thickness ratio was about
39:1. Their behaviour is compared to that of an epoxy carbon-fibre laminate. It was concluded that the thermoplastic comlx~itcs were superior to epoxy composites in suppressing delamination failure in bending. However, the thermoplastic composites were more prone to longitudinal compression failure. Relation between work of fracture and fracture toughness of short fibre-reinfeceed polymers Lauke, B. and Pompe, W. Composites Science and Technology Vol 31 No 1 (1988~ p p 25-33 Mathematical expressions are derived for w, the work of fracture, and G¢, fracture toughness, for short fibre-reinforced polymers by first determining the crack-resistance curve. It is shown that both parameters are necessary to describe failure behaviour; Gc for crack instability, or strength; and w as the energy necessary to drive the crack through the sample. In many cases, the work of fracture was found to be much higher than the fracture toughness. Simulation of the percolation threshold in metal fibre loaded conductive bridge polymer composites Bridge, B. Journal o f Materials Science Letters Vol 7 No 6 (1988) pp 663-665 In order to overcome the difficulties in the calculation of the perculation threshold (the volume fraction of conducting fibres in a non-conducting matrix at which conductivity increases rapidly), the author has constructed a model of the electrical behaviour of such a composite. It was found that the model's behaviour agreed well with resistivity measurements in a real material. A study of the development of impact damage in cross-ply carbon fibre/PEEK laminates using acoustic emission Nixon, J. A., Phillips, M. G., Moore, D. R. and Prediger, R. S. Composites Science and Technology Vo131 No I (1988) pp 1-14 Instrumented falling weight impact tests were performed on [0/90h0s APC-2/AS4 laminates to investigate damage development. It was observed that at an input energy of 4.9 J the onset of delamination occurred. The specimens were afterwards subjected to four-point bending tests with acoustic emission (AE) monitoring and the critical level of impact energy was seen to be associated with a sharp change in the evolution of AE under increasing load. The AE behaviour was shown to be different for laminates with and without delamination, indicating that A E may be used for the detection of sub-critical damage and, with further development, the rest may be made semi-quantitative. Surface pretreatment and adhesion of ti~rmoplastic fibre-composites Kodokian, G. K. A. and Kinloch, A. J. Journal o f Materials Science Letters Vol 7 No 6 (1988) pp 625-627 The effects of surface pretreatment on the fracture toughness of adhesively bonded APC-2 (carbon fibre/PEEK) and 913C XAS (carbon-fibre/epoxy) are reported. The surface pretreatments were: abrasion, moulding, next to aluminium foil (to reduce release agent pick-up), acid etch and corona dis-, charge. Rubber-toughened epoxy and PEEK were used in adhesives. For all surface
COMPOSITES. JANUARY 1989)
treatments in the case of the APC-2 material, it was found that epoxy gave poor bond strengths. It is suggested that this is due to the poor bond strengths. It is suggested that this is due to the poor wettability and intrinsic adhesion of the PEEKmaterial. Use of Weibull statistics to quantify specimen size effects in fatigue of GRP Crowther, M. F. and Starkey, M. S.
Composites Science and Technology Vol 31 No 2 (1988) pp 87-95 Data are presented to show that changing specimen size has considerable effect on the fatigue life of unidirectional GRP. Weibull statistics are used in an attempt to quantify the change in fatigue life that would be expected from size effects alone and the predictions tested against experimental data obtained for unidirectional glass fibre-
reinforced epoxy composites tested in flexure. It is shown that, where material and processing variables are kept constant, the model predicts the change in fatigue life with stressed volume with reasonable accuracy. It is stated that the model will also allow the effect attributable to change in dimensions of a specimen to be separated from the effects attributable to a change in material properties.
Abstracts of British Patents are prepared by Dr F. R. Jones, Department of Ceramics, Glasses and Polymers, University of Sheffield, UK
UK PATENTS COMPONENTS Bonding thermoplastic materials (The Welding Institute, UK) GB 2 200 590 A (10 August 1988) iCarbon fibre thermoplastic prepreg is used as the adhesive interlayer for a fusion weld whereby the fibres act as the heating element. I i
!Joining earl~n-c~rbon materials (Acurex Corp, USA) GB 2 201 122.4 (24 August 1988) A carhonisable interlayer such as pitch is used to stabilise a compression joint between two carbon fibre reinforced carbon materials.
GB 2 201 117 A (24 August 1988) A polyurethane foam is used as an in situ mandrel or for filling FRP layed-up onto an inflatable mandrel. The manufacture of lightweight extruded structural profile (M, J. Hewitt, UK) GB 2 202 180 A/GB 2 202 182 A (21 September 1988) A technique for continuous pultrusion of a graded particulate filled GRP sheath is described whereby the fillers are vacuum compacted sequentially with the finer fillers filling the interstices between the coarse filler particles. The particles are normally foamed to give a lightweight profile.
US PATENTS COMPONENTS
WA TERIALS CremJi~able polyphenylene oxide resin commtttm Matsushita Electric Works Ltd, Japan) ~B 2 200 128 A (27 July 1988) The described matrix has applications for :omposite laminates as printed circuit board mbstrates, with enhanced heat and chemical resistance. Polyimtde-siloxanes method of making and General Electric Company, USA) GB 2 200 647 A (10 August 1988) These condensation polymers have applications in semiconductor devices and composites. Heat insulating laminates (Man Technologic GmbH, FRG) GB 2 201 373 A (1 September 1988) Ceramic material for use at 1000°C and above is made from reflective layers consisthag of a subtrate of impregnated, fired ceramic fibres and a noble metal interdispersed with alumina fibrous wadding.
PROCESSES ~ n g process for composite hockey stidm (Charing Inn Aluminium Industry Co Ltd, Talwan)
COMPOSITES. JANUARY 1989
Composite thread line sails Conrad, P. G. (Sobstad Sailmakers Incorporated, Old Saybrook, CT, USA) US Pat 4 708 080 (24 November 1987) A sail, with a head, a tack, and a clew, which in use has principal stress lines is made up from a number of joined panels. Each panel is a laminate consisiting of at least two layers between which is non-woven, force-bearing thread material predeterminedly disposed along the lines of stress. Club-head Kobayashi, M. (Maruman Company Limited, Tokyo, Japan) US Pat 4 708 347 (24 November 1987) A golf club head made from a number of separate portions is described. The main body, made from fibre-reinforced plastic, contains a weight of heavy material and is attached to a metal sole. Extruder die for extrusion of a thermoplastic laminate Reifenhfiuser, H., Reitemeyer, P., Krumm, K. and Beisemann, H. (Reifenhauser GmbH and Company Maschinenfabrik, Troisdorf, FRG) US Pat 4 708 618 (24 November 1987) A die for the extrusion of a multilayer thermoplastic laminate in the form of a foil or plate is described. Environmentally protected electrical contact terminal arrangement for a plastic-metalplastic laminated cycle fender
Belka, H. (ESGE-Marby GmbH and Company KG, Bielefeld, FRG) US Pat 4 708 665 (24 November 1987) The cycle fender comprises two layers of plastic within which is embedded a layer of metal foil. Within the fender is a shaft filled with ribbed rivet-shaped metal, the head of which rests upon the upper plastic layer and the body of which contains and provides electrical contact with the metal foil. Method of making a flexible bearing McGregor, J. D. (Morton Thiokol Incorporated, Chicago, IL, USA) US Pat 4 708 757 (24 November 1987) The bearing comprises first and second rigid end rings with flexible laminations between; the laminations consisting of alternating layers of elastomeric material and rigid reinforcement shims made of fabric material impregnated with resin. The whole bearing shape conforms to surfaces of concentric spheres. The bearing is made by first pressing and compacting each uncured resin impregnated fabric reinforceinent into the required shape. The bearing is then assembled in a mould and subjected to heat and pressure to cure the reinforcement and vulcanize the elastomeric material.
MATERIALS Zirconium metal matrix-silicon carbide coin. posite nuclear reactor components Ferrari, H, M. (Westinghouse Electric Corporation, Pittsburgh, PA, USA) US Pat 4 707 330 (17 November 1987) Metallic components, including fuel cladding, control rods, rod guide thimbles, grids and channels, of a nuclear reactor are made from a metal matrix composite comprising 90-60 vol% Zr or a zirconium alloy (containing <5% alloying element) reinforced with 10-40 vol% SiC whiskers. Bicomponent ceramic fibres Rambosek, G. M. (Minnesota Mining and Manufacturing Company, St Paul, MN, USA) US Pat 4 707 399 (17 November 1987) A continuous, bicomponent, non-vitreous ceramic fibre, circular, oval or rod-like in cross-section comprises two ceramic components extending longitudinally side-by-side, each component being derived from a
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