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Fatigue of boron-aluminium and carbon-aluminium fibre composites
METAL MA TRICES The ageing response of AI-Cu and AI-Cu-Mg directionally solidified eutectic Rhodes, C. G. and Garomong, G. Metallurgical Transactions, Vol 3, No 7, p 1861 (Jul 1972) A study was made of the ageing of the unidirectionally solidified A1-Cu and AI-Cu-Mg eutectic alloys after they had been solutionized at 535°C and quenched. Examination by electron microscopy showed that the aluminium-based or-phase in the composite aged in a similar manner to dilute aluminium alloys of a corresponding composition. It was found that the tensile and compressive strengths of the AI-Cu composite were increased by a factor of two when it was aged at 180°C for 10 hours.
Fatigue of boron-aluminium and carbonaluminium fibre composites Baker, A. A., Braddick, D. M. and Jackson, P. W. Journal o f Materials Science, 1Iol 7, No 7, pp 747-762 (Jul 1972) The results of some reversed bending fatigue studies on carbon-aluminium and boron-aluminium alloy composites are given. Matrix fatigue was found to be the primary cause of damage suffered by these composites but some evidence was found for induced fibre failure in the boron composites under high-stress/ low-cycle conditions.
Hysteresis in the composite-to-dendrite transition off-eutectic Sn-Pb alloys Verhoeven, J. D. and Gibson, E. D. Metallurgical Transactions, Vol 3, No 7, p 1893 (Jul 1972) The composite-to-dendrite transition in directionally solidified Sn-Pb alloys was studied under conditions of variable solidification rate. During solidification in which the growth rate was progressively increased the dendrites began to form at a growth rate higher than that at which they began to disappear during solidification in which the rate was progressively decreased. The findings are discusscd in relation to recent experimental and theoretical work.
The multiple yield phenomenon in singlefiber composites of iron in copper Garmong, G. Metallurgical Transactions,
Vol 3, No 7, p 1919 (Jul 1972) The load-elongation behaviour was studied of single-fibre composites formed of copper wire 'reinforced' with a core of iron. The composites exhibited multiple yield, each yield event being caused by the formation of a Ltiders band in the iron. The number of Lfiders bands that formed decreased with increasing volume fraction of the iron up to a fraction of 0-31. Above this fraction only one band usually formed. These observations were explained in terms of a model based on the assumption that the Ltiders strain caused strain between fibre and matrix ahead of the band.
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On the rod to blade transition in the AI-AI3Ni eutectic Smartt, H. B. and Courtney, T. H. Metallurgical Transactions, 1Iol 3, No 7, p 2000 (Jul 1972) A study was made of the microstructure of AI-AI3 Ni composites prepared by unidirectional solidifcation of the eutectic at different growth rates. It was found that when the growth rate was decreased from 10 cm/h to 5 em/h, a transverse section of the composites indicated that the AI3Ni fibres changed their form from rod to blade-like. When the specimens were deep etched and viewed in the scanning electron microscope it was seen that the blade-like cross-sections were due to the micro-section passing through the junctions of branched rods. Ultrasonic velocity measurement of elastic constants of AI-AI3Ni unidirectionally solidified eutectic Gravel, J. V. and Cost, J. R. Metallurgical Transactions, Vol 3, No 7, p 19 73 (Jul 1972) The pulse-echo-overlap method was used with apparent success to determine the velocity of sound waves in a composite of AI3Ni fibres in an aluminium matrix, prepared by unidirectional solidification of the eutectic. The measurements of ultrasonic velocity were used to determine various elastic constants of the composite. The Young's modulus determined in this way was in good agreement with previously reported values determined by other means. The results were also used to derive elastic constants of the AI3Ni fibres.
RESIN MA TRICES Comoform, an advance in the cold moulding process for glass reinforced polyester Zion, E. M. and Williams, G. L. Reinforced Plastics, Vol 16, No 5, p 135 (May 1972) In this review article cold press moulding and an extension of this process - Comoform (Cold moulding Thermoforming) are compared in terms of cost, physical properties and appearance of products. it is concluded that, although cold moulding is not used to any great extent as yet, it does have significant economic advantages when the component to be made requires a good surface on both sides and when volume production does not exceed 8 million items. Extrusion of thermosetting materials Kanneblcy, G. Plastics and Polymers, Vol 40, No 145, p 13 (Feb 1972) A process for the production of extruded thermosetting resin products reinforced with long glass fibres is described. This process (pultrusion) may be operated vertically, horizontally or on an inclined plane depending on the desired crosssection. A number of applications are described. Transition metal-modified matrix resins for composite materials Neuse, E. W. Journal of Materials Science. Vol 7. No 6, pp 708- 9 (Jun 19 72)
Previous efforts to improve such properties as abrasion resistance, electric conductance and magnetic performance of a resin composite matrix by incorporation of metallic particles have met with only limited success, mainly as a result of low interfacial adhesion causing a decrease in matrix strength. More success in this field is reported here, where organometallic complexes have been blended with phenolic and epoxy resins. Particularly encouraging properties have been obtained with iron and chromium complexes and this gives hope for similar results with other transition metals.
STRUCTURES Deflection of polypropylene sandwich mouldings under bending loads Ogorkievicz, R. M. and Sayigh, A. A. M. Plastics and Polymers, Vol 40, No 146, p 64 (Apr 1972) The mechanical characteristics of thermoplastic sandwich mouldings, which are in principle particularly suitable for bendhag load applications, have been analysed. The initial step in such an analysis is the examination of the sandwich structure rather than its components. The necessary minimum of information about the behaviour of the skin and core components was also obtained, thus enabling a comparison to be made between theoretical and environmental observations of the deflection behaviour of the sandwich beams. Good agreement was obtained using equations based on stress functions but not by using an equivalent section approach. The effect of thickness and temperature on heat transfer through foamed plastics Jones, T. T. Plastics and Polymers, Vol 40,
No 145, p 33 (Feb 1972) The mechanisms of heat transfer through foamed plastics are considered. For a discrete bubble system convection currents within cells will contribute to heat transfer, but this effect should be reduced by a reduction in bubble size. As the proportion of gas phase is increased the conductivity of the foam also increases. The evidence now suggests that provided the cell size is small enough to limit convection then the primary cause of this effect is radiation. However, the ratio of conducted to radiated heat flow depends on the temperature, sample thickness, density and cell size. The physical properties of foamed plastics and their dependence on structure Baxter, S. and Jones, T. T. Plastics and
Polymers, 1Iol 40, No 146, p 69 (Apr 1972) The dependence of thermal conductivity, permeability and mechanical properties of foamed plastics on the density and structure of the foam is described. In addition to foams containing discrete bubbles and interconnected pores, those with a continuous gas phase such as glass wool blankets are also considered for comparison. It is shown that the theoretical predictions of Kerner can frequently be used to assess the physical properties of such foamed materials thus eliminating much experimentation.
COMPOSITES. JANUARY 1973
Fatigue of boron-aluminium and carbonaluminium fibre composites Baker, A. A., Braddick, D. M. and Jackson, P. W. Journal o f Materials Science, 1Iol 7, No 7, pp 747-762 (Jul 1972) The results of some reversed bending fatigue studies on carbon-aluminium and boron-aluminium alloy composites are given. Matrix fatigue was found to be the primary cause of damage suffered by these composites but some evidence was found for induced fibre failure in the boron composites under high-stress/ low-cycle conditions.
Hysteresis in the composite-to-dendrite transition off-eutectic Sn-Pb alloys Verhoeven, J. D. and Gibson, E. D. Metallurgical Transactions, Vol 3, No 7, p 1893 (Jul 1972) The composite-to-dendrite transition in directionally solidified Sn-Pb alloys was studied under conditions of variable solidification rate. During solidification in which the growth rate was progressively increased the dendrites began to form at a growth rate higher than that at which they began to disappear during solidification in which the rate was progressively decreased. The findings are discusscd in relation to recent experimental and theoretical work.
The multiple yield phenomenon in singlefiber composites of iron in copper Garmong, G. Metallurgical Transactions,
Vol 3, No 7, p 1919 (Jul 1972) The load-elongation behaviour was studied of single-fibre composites formed of copper wire 'reinforced' with a core of iron. The composites exhibited multiple yield, each yield event being caused by the formation of a Ltiders band in the iron. The number of Lfiders bands that formed decreased with increasing volume fraction of the iron up to a fraction of 0-31. Above this fraction only one band usually formed. These observations were explained in terms of a model based on the assumption that the Ltiders strain caused strain between fibre and matrix ahead of the band.
48
On the rod to blade transition in the AI-AI3Ni eutectic Smartt, H. B. and Courtney, T. H. Metallurgical Transactions, 1Iol 3, No 7, p 2000 (Jul 1972) A study was made of the microstructure of AI-AI3 Ni composites prepared by unidirectional solidifcation of the eutectic at different growth rates. It was found that when the growth rate was decreased from 10 cm/h to 5 em/h, a transverse section of the composites indicated that the AI3Ni fibres changed their form from rod to blade-like. When the specimens were deep etched and viewed in the scanning electron microscope it was seen that the blade-like cross-sections were due to the micro-section passing through the junctions of branched rods. Ultrasonic velocity measurement of elastic constants of AI-AI3Ni unidirectionally solidified eutectic Gravel, J. V. and Cost, J. R. Metallurgical Transactions, Vol 3, No 7, p 19 73 (Jul 1972) The pulse-echo-overlap method was used with apparent success to determine the velocity of sound waves in a composite of AI3Ni fibres in an aluminium matrix, prepared by unidirectional solidification of the eutectic. The measurements of ultrasonic velocity were used to determine various elastic constants of the composite. The Young's modulus determined in this way was in good agreement with previously reported values determined by other means. The results were also used to derive elastic constants of the AI3Ni fibres.
RESIN MA TRICES Comoform, an advance in the cold moulding process for glass reinforced polyester Zion, E. M. and Williams, G. L. Reinforced Plastics, Vol 16, No 5, p 135 (May 1972) In this review article cold press moulding and an extension of this process - Comoform (Cold moulding Thermoforming) are compared in terms of cost, physical properties and appearance of products. it is concluded that, although cold moulding is not used to any great extent as yet, it does have significant economic advantages when the component to be made requires a good surface on both sides and when volume production does not exceed 8 million items. Extrusion of thermosetting materials Kanneblcy, G. Plastics and Polymers, Vol 40, No 145, p 13 (Feb 1972) A process for the production of extruded thermosetting resin products reinforced with long glass fibres is described. This process (pultrusion) may be operated vertically, horizontally or on an inclined plane depending on the desired crosssection. A number of applications are described. Transition metal-modified matrix resins for composite materials Neuse, E. W. Journal of Materials Science. Vol 7. No 6, pp 708- 9 (Jun 19 72)
Previous efforts to improve such properties as abrasion resistance, electric conductance and magnetic performance of a resin composite matrix by incorporation of metallic particles have met with only limited success, mainly as a result of low interfacial adhesion causing a decrease in matrix strength. More success in this field is reported here, where organometallic complexes have been blended with phenolic and epoxy resins. Particularly encouraging properties have been obtained with iron and chromium complexes and this gives hope for similar results with other transition metals.
STRUCTURES Deflection of polypropylene sandwich mouldings under bending loads Ogorkievicz, R. M. and Sayigh, A. A. M. Plastics and Polymers, Vol 40, No 146, p 64 (Apr 1972) The mechanical characteristics of thermoplastic sandwich mouldings, which are in principle particularly suitable for bendhag load applications, have been analysed. The initial step in such an analysis is the examination of the sandwich structure rather than its components. The necessary minimum of information about the behaviour of the skin and core components was also obtained, thus enabling a comparison to be made between theoretical and environmental observations of the deflection behaviour of the sandwich beams. Good agreement was obtained using equations based on stress functions but not by using an equivalent section approach. The effect of thickness and temperature on heat transfer through foamed plastics Jones, T. T. Plastics and Polymers, Vol 40,
No 145, p 33 (Feb 1972) The mechanisms of heat transfer through foamed plastics are considered. For a discrete bubble system convection currents within cells will contribute to heat transfer, but this effect should be reduced by a reduction in bubble size. As the proportion of gas phase is increased the conductivity of the foam also increases. The evidence now suggests that provided the cell size is small enough to limit convection then the primary cause of this effect is radiation. However, the ratio of conducted to radiated heat flow depends on the temperature, sample thickness, density and cell size. The physical properties of foamed plastics and their dependence on structure Baxter, S. and Jones, T. T. Plastics and
Polymers, 1Iol 40, No 146, p 69 (Apr 1972) The dependence of thermal conductivity, permeability and mechanical properties of foamed plastics on the density and structure of the foam is described. In addition to foams containing discrete bubbles and interconnected pores, those with a continuous gas phase such as glass wool blankets are also considered for comparison. It is shown that the theoretical predictions of Kerner can frequently be used to assess the physical properties of such foamed materials thus eliminating much experimentation.
COMPOSITES. JANUARY 1973