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SiC matrix composite at elevated temperature
Itt talx m fvtq Prepared by M. E. Adams, L. Boniface and A. Pryce
CEMENT MA TRICES
CERAMIC FIBRES
Bond of deformed reinforcing bar embedded in steel fibre reinforced concrete Rostfisy, F. S. and Hartwich, K. The
Calorimetric evaluation of the effects of SiC concentration on the precipitation processes in SiC particulate reinforced 7091 aluminium Petty-Gallis, J. L. and Goolsby, R. D.
International Journal o f Cement Composites and Lightweight Concrete Vol 10 No 3 (August 1988) pp 151-158 Tests devised to help identify the role of reinforcing steel fibres in concrete that is also reinforced by a standard hot-rolled bar of irregular shape are described. Two types of commercially-available steel fibre - straight or hooked - were investigated. It was found that the bond strength of the bar to concrete was not enhanced by the presence of steel fibres. However, the post-peak ductility of specimens failing by splitting was greatly improved by fibre addition. Thus, it is concluded that the observed reduction of crack width and deformation of reinforced concrete bending members with steel fibre addition is caused by the transfer of tensile force across primary cracks by the fibres, acting as randomly oriented reinforcing bars. High strength lightweight concrete for use in offshore structures: utilisation of fly ash and silica fume Seabrook, P. I. amd Wilson, H. S. The
International Journal o f Cement Composites and Lightweight Concrete Vol 10 No 3 (August 1988) pp 183-192 The results obtained in the second phase of on-going research into lightweight concrete suitable for use in offshore structures in Arctic conditions are reported. The mixtures comprised fine and coarse aggregates and cementitious materials which included fly ash and silica fume. It was found necessary to introduce the silica fume in a water slurry with superplasticiser as dispersant to obtain a good dispersion in the mixture but that the addition of silica fume significantly improved the strength of the resultant concrete. Load-deformation behaviour of planar and curved microconcrete plates reinforced with melt extract fibres Kearns, C. F. and McConnell, G. M. The
International Journal of Cement Composites and Lightweight Concrete Vol 10 No 3 (August 1988) pp 159-166 The results of static load tests carried out on simply-supported planar and curved microconcrete plates reinforced with melt extract stainless steel fibres are presented. It is shown that the addition of the fibre reinforcement achieves a stable ductile postcracking response in the plates. The beneficial effect of curvature on the structural behaviour of the plates is also indicated.
COMPOSITES
. SEPTEMBER
1989
Journal o f Materials Science Vo124 (1989)pp 1439-1446 Differential scanning calorimetry is a useful technique to tailor thermal and thermomechanical properties of metal matrix composites to produce the required ultimate properties. The present paper characterises the precipitation reactions in the discontinuous SiC reinforced 7091 aluminium composite, paying particular attention to the effect of processing variables such as SiC concentration, temperature, time and sequences. The results indicate that the presence of SiC significantly alters the transformation kinetics of the aluminium alloy, increasing the temperature at which GPI zones revert at their maximum rate. In addition increasing the SiC content decreases the temperature at which GPI and GPII zones precipitate and equilibrium of phase dissolution occurs. Transformation mechanisms have been proposed for these observations. Evidence for a silicon oxycarbide phase in the Nicalon silicon carbide fibre. Porte, L. and Sarte, A. Journal o f Materials
Science Vol 24 (1989) pp 271-275 There is at present considerable interest in the use of silicon carbide fibres as the reinforcement of composite materials in high temperature applications. The Nicalon fibre (trade mark of the Nippon Carbon Company) studied here consists of primary SiC and certain other phases which influence its behaviour. The present paper considers the role of oxygen atoms and how they are incorporated into the fibre network using X-ray photoelectron spectroscopy (XPS). Results indicate that only a small proportion of the total oxygen content exists as SiO2 incorporated in the fibre. Larger quantities are found however in a silicon oxycarbide ternary phase, intermediary to SiC and SiOz. This phase, probably originating from the polymer precursor, could be an important factor governing the thermomechanical properties of the Nicalon fibre.
CERAMIC MA TRICES Fibre reinforced glasses Hegeler, H. and Briickner. Journal of Materials Science Vol 24 (1989) 1191-1194. The processing of fibre reinforced glasses can
be achieved by two distinct routes; the slurry method and the sol-gel technique. The present paper proposes a method using the Nicalon fibre reini ~rced borosilicate glass system which combines ideas from both processes, thus eliminating the use of a binder. The resulting prepregs are hot pressed and the influence of a number of processing variables on bend strength is examined. Fracture resistance of a TiB2 particle/SiC matrix composite at elevated temperature. Jenkins, M. G., Salem, J. A. and Seshadri,
S. G. Journal o f Composite Materials Vo123 No 1 (January 1989) pp 77-91 The fracture behaviour of a commercial composite of particulate TiB2 reinforced SiC matrix is studied in the temperature range 20-1400°C. Crack mouth opening displacement (CMOD) is monitored in straightnotched and chevron-notched three-point bend specimens using a laser interferometric strain gauge to determine R-curves, fracture toughness and work of fracture. The chevron-notched configuration is subsequently adopted since the sharper notch gives stable crack growth and more reliable work of fracture results and R-curves. Strength is found to be independent of temperature but the fracture parameters show a decrease with increasing temperature, related to thermally activated mechanisms. Microscopic observations of fracture surfaces, microstructure and oxidation coatings are compared for asreceived samples and samples tested up to 1400°C. In as-received samples, microcracks develop at the TiB2 particle/matrix interface which divert the fracture path around particles, producing a rough surface. At high temperature, the smooth fracture surface indicates that the particles are less effective in resisting crack growth. The change in crack mechanism at elevated temperature is explained in terms of the relief of residual stresses which otherwise enhance microcracking. X-ray analysis of the oxide layer shows TiO2 with SiO2 which increases in thickness with increasing temperature, leading to attack of the material beneath to variable depths. Silicon carbide fibre reinforced glass ceramic composite tensile properties at e l e v a t e d temperature. Prewo, K. M., Johnson, B. and Starrett, S.
Journal o f Materials Science Vo124 (1989) pp 1373-1379 Fibre reinforced glass ceramic composites offer an alternative to light metal alloys in many elevated temperature applications. For this reason there has been much interest in developing such materials as the Nicalon fibre (trade mark of the Nippon Carbon Company) reinforced LAS matrix composite, which is studied in this paper. The
493
CEMENT MA TRICES
CERAMIC FIBRES
Bond of deformed reinforcing bar embedded in steel fibre reinforced concrete Rostfisy, F. S. and Hartwich, K. The
Calorimetric evaluation of the effects of SiC concentration on the precipitation processes in SiC particulate reinforced 7091 aluminium Petty-Gallis, J. L. and Goolsby, R. D.
International Journal o f Cement Composites and Lightweight Concrete Vol 10 No 3 (August 1988) pp 151-158 Tests devised to help identify the role of reinforcing steel fibres in concrete that is also reinforced by a standard hot-rolled bar of irregular shape are described. Two types of commercially-available steel fibre - straight or hooked - were investigated. It was found that the bond strength of the bar to concrete was not enhanced by the presence of steel fibres. However, the post-peak ductility of specimens failing by splitting was greatly improved by fibre addition. Thus, it is concluded that the observed reduction of crack width and deformation of reinforced concrete bending members with steel fibre addition is caused by the transfer of tensile force across primary cracks by the fibres, acting as randomly oriented reinforcing bars. High strength lightweight concrete for use in offshore structures: utilisation of fly ash and silica fume Seabrook, P. I. amd Wilson, H. S. The
International Journal o f Cement Composites and Lightweight Concrete Vol 10 No 3 (August 1988) pp 183-192 The results obtained in the second phase of on-going research into lightweight concrete suitable for use in offshore structures in Arctic conditions are reported. The mixtures comprised fine and coarse aggregates and cementitious materials which included fly ash and silica fume. It was found necessary to introduce the silica fume in a water slurry with superplasticiser as dispersant to obtain a good dispersion in the mixture but that the addition of silica fume significantly improved the strength of the resultant concrete. Load-deformation behaviour of planar and curved microconcrete plates reinforced with melt extract fibres Kearns, C. F. and McConnell, G. M. The
International Journal of Cement Composites and Lightweight Concrete Vol 10 No 3 (August 1988) pp 159-166 The results of static load tests carried out on simply-supported planar and curved microconcrete plates reinforced with melt extract stainless steel fibres are presented. It is shown that the addition of the fibre reinforcement achieves a stable ductile postcracking response in the plates. The beneficial effect of curvature on the structural behaviour of the plates is also indicated.
COMPOSITES
. SEPTEMBER
1989
Journal o f Materials Science Vo124 (1989)pp 1439-1446 Differential scanning calorimetry is a useful technique to tailor thermal and thermomechanical properties of metal matrix composites to produce the required ultimate properties. The present paper characterises the precipitation reactions in the discontinuous SiC reinforced 7091 aluminium composite, paying particular attention to the effect of processing variables such as SiC concentration, temperature, time and sequences. The results indicate that the presence of SiC significantly alters the transformation kinetics of the aluminium alloy, increasing the temperature at which GPI zones revert at their maximum rate. In addition increasing the SiC content decreases the temperature at which GPI and GPII zones precipitate and equilibrium of phase dissolution occurs. Transformation mechanisms have been proposed for these observations. Evidence for a silicon oxycarbide phase in the Nicalon silicon carbide fibre. Porte, L. and Sarte, A. Journal o f Materials
Science Vol 24 (1989) pp 271-275 There is at present considerable interest in the use of silicon carbide fibres as the reinforcement of composite materials in high temperature applications. The Nicalon fibre (trade mark of the Nippon Carbon Company) studied here consists of primary SiC and certain other phases which influence its behaviour. The present paper considers the role of oxygen atoms and how they are incorporated into the fibre network using X-ray photoelectron spectroscopy (XPS). Results indicate that only a small proportion of the total oxygen content exists as SiO2 incorporated in the fibre. Larger quantities are found however in a silicon oxycarbide ternary phase, intermediary to SiC and SiOz. This phase, probably originating from the polymer precursor, could be an important factor governing the thermomechanical properties of the Nicalon fibre.
CERAMIC MA TRICES Fibre reinforced glasses Hegeler, H. and Briickner. Journal of Materials Science Vol 24 (1989) 1191-1194. The processing of fibre reinforced glasses can
be achieved by two distinct routes; the slurry method and the sol-gel technique. The present paper proposes a method using the Nicalon fibre reini ~rced borosilicate glass system which combines ideas from both processes, thus eliminating the use of a binder. The resulting prepregs are hot pressed and the influence of a number of processing variables on bend strength is examined. Fracture resistance of a TiB2 particle/SiC matrix composite at elevated temperature. Jenkins, M. G., Salem, J. A. and Seshadri,
S. G. Journal o f Composite Materials Vo123 No 1 (January 1989) pp 77-91 The fracture behaviour of a commercial composite of particulate TiB2 reinforced SiC matrix is studied in the temperature range 20-1400°C. Crack mouth opening displacement (CMOD) is monitored in straightnotched and chevron-notched three-point bend specimens using a laser interferometric strain gauge to determine R-curves, fracture toughness and work of fracture. The chevron-notched configuration is subsequently adopted since the sharper notch gives stable crack growth and more reliable work of fracture results and R-curves. Strength is found to be independent of temperature but the fracture parameters show a decrease with increasing temperature, related to thermally activated mechanisms. Microscopic observations of fracture surfaces, microstructure and oxidation coatings are compared for asreceived samples and samples tested up to 1400°C. In as-received samples, microcracks develop at the TiB2 particle/matrix interface which divert the fracture path around particles, producing a rough surface. At high temperature, the smooth fracture surface indicates that the particles are less effective in resisting crack growth. The change in crack mechanism at elevated temperature is explained in terms of the relief of residual stresses which otherwise enhance microcracking. X-ray analysis of the oxide layer shows TiO2 with SiO2 which increases in thickness with increasing temperature, leading to attack of the material beneath to variable depths. Silicon carbide fibre reinforced glass ceramic composite tensile properties at e l e v a t e d temperature. Prewo, K. M., Johnson, B. and Starrett, S.
Journal o f Materials Science Vo124 (1989) pp 1373-1379 Fibre reinforced glass ceramic composites offer an alternative to light metal alloys in many elevated temperature applications. For this reason there has been much interest in developing such materials as the Nicalon fibre (trade mark of the Nippon Carbon Company) reinforced LAS matrix composite, which is studied in this paper. The
493