- Email: [email protected]
Composition-microstructure-property relationships in ceramic monofilaments resulting from the pyrolysis of a polycarbosilane precursor at 800 to 1400°C
Literature survey Prepared by M.R. Alexander, J. Collins, M.D. Glendenning and A.J. Host)/, University of Sheffield, UK CARBON FIBRES The strength of pitch-based carbon fibre at high temperature Tanabe, Y., Yasuda, E., Bunsell, A.R., Favry, Y., Inagaki, M. and Sakai, M. Journal o f Materials Science Vol 26 No 6 (1991) pp 1601-1604 The mechanical properties of pitch-based carbon fibres have been measured at temperatures up to 1300°C in both nitrogen and air atmospheres, the experimental difficulties associated with the high temperature testing of fibres having been overcome. The mechanical properties of these fibres were found to improve up to 1300°C. It is suggested that three defect populations control the fibre properties over the temperature range studied.
CARBON MA TRICES Failure analysis and damage initiation in carbon-carbon composite materials under three-point bending Copp, P.D., Dendis, J.C. and Mall, S. Journal o f Composite Materials Vol 25 No 5 (1991) pp 593-608 This paper investigates the damage and resulting failure modes caused in carbon/ carbon composites by the contact stresses caused by attaching them to other components with fasteners. Fastening is simulated using the three-point bend test, which the simplest contact arrangement available. Damage initiation and failure mechanisms are studied for woven uncoated carbon/ carbon composites in long and short beam geometries.
CERAMIC FIBRES Composition-microstruct ure-property relationships in ceramic monofilaments resulting from the pyrolysis of a polycarbosilane precursor at 800 to 1400°C Bouillon, E., Mocaer, D., Villencuve, J.F., Pailler, R., Naslain, R., Monthioux, M., Oberlin, A., Guimon, C. and Pfister, G. Journal o f Materials Science Vol 26 No 6 (1991) pp 1517-1530 Monofilaments have been drawn from a polycarbosilane melt, cross-linked with oxygen and pyrolysed between 800°C and 1400~C. The processes taking place during pyrolysis have been examined and the resulting fibres extensively characterized. The fibres are composed of amorphous material that is stable up to about 1100~C. Above this temperature a crystalline state evolves, resulting in a drop in the tensile strength. The mechanisms involved in pyrolysis and the amorphous to crystalline transition are discussed.
472
CVD Mo, W and Cr oxycarbide, carbide and silicide coatings on SiC yarn Kmetz, M., Tan, B.J., Willis, W., Suib, S. and Galasso, F.S. Journal o f Materials Science Vol26 No 8 (1991) pp 2107-2110 The possibility of coating silicon carbide fibres using Mo, W and Cr carbonyl systems has been explored. Fibres were successfully coated with the oxycarbides without degradation. Heat treatment in nitrogen converted the oxycarbides to metals and further heat treatment in SiCI 4 produced silicide coatings. A longer coating time was used to form a SiC/tungsten oxycarbide composite which had a tensile strength of 193 MPa. Silsesquioxane-drived ceramic fibres Hurwitz, F.I., Farmer, S.C., Tcrepka, F.M. and Leonhardt, T.A. Journal o f Materials Science Vo126 No 5 (1991) pp 1247-1252 Fibres have been drawn from blends of commercially available siisesquioxane polymers, before prolysing in an argon atmosphere to yield an Si-C-O fibre. The blends have been characterized using differential scanning calorimetry and thermogravimetric analysis. The structure and chemistry of the fibres has been examined by SEM, TEM and microanalysis. The microstructure was rather inhomogeneous on the scale of a few microns, which is attributed to the low miscibility of the polymers used. On the namometre scale phase-separated microstructures were observed. Depending on the blend of polymers used and the pyrolysis conditions, both silicon oxycarbide and SiC fibres have been produced. Testing E-glass bundles using acoustic emission Cowking, A., Attou, A., Siddiqui, A.M., Sweet, M.A.S. and Hill, R. Journal o f Materials Science Vo126 No 5 (1991) pp 1301-1310 Acoustic emission has been used to follow individual fibre failures in a lubricated bundle of E-glass fibres. By this method it was found possible to generate the fracture stress distribution of the fibres in the bundle. While these results may be fitted with Weibull statistics, the method described does not rely on this and could be applied where the distribution does not fit such an expression or where failure is not perfectly elastic.
CERAMIC MA TRICES Determination of fibre-matrix interfacial properties in ceramic-matrix composites by a fibre push-out technique Singh, R.N. and Sutcu, M. Journal o f Materials Science I/ol26 No 9 (1991) pp 2547-2556 A concentric cylinder model is used to interpret indenter load/displacement curves for fibre push-out tests in ceramic-matrix composites. The model assumes that the interface is partially bonded and partially frictionally coupled. A change of slope of the loading curve is shown to correspond to bonding at
COMPOSITES. NOVEMBER 1991
the interface, whereas little change is predicted for a frictionally coupled interface. This model provides a method for determining the interfacial debond energy and interfacial shear strength from fibre push-out tests. The predictions of this model are compared with test results on Zircon/SiC composites uniaxially reinforced with uncoated or BN-coated SiC microfilaments. The results suggest that the fibre/matrix interfaces of these composites are frictionally coupled. Discrete failure mode detection in a woven SiC cloth reinforced glass composite Krynicki, J.W., Green, R.E. and Nagle, D.C. Journal o f Materials Science Vo126 No 8 (1991) pp 2184-2188 A single layer of SiC cloth has been used to reinforce a borosilicate glass. The fracture in three-point bend of this material has then been observed optically, to try to explain anomalies in the load/deflection curves. Acoustic emission was also used to monitor the fracture process. The failure mode observed by these techniques was of a first crack starting on the tensile face and propagating to the fibre layer; at this point a second crack initiated on the opposite side of the fibre layer which is eventually put in tension as fibre pull-out occurs. Elevated temperature mechanical properties of continuous metallic glass ribbon-reinforced glass-ceramic matrix composites Vaidya, R.U. and Subramanian, K.N. Journal o f Materials Science Vol 26 No 5 (1991) pp 1391-1394 Three-point bend tests have been carried out at temperatures up to 500°C on samples of a glass-ceramic matrix composite reinforced with a small volume fraction of continuous metallic ribbon. At room temperature significant improvements are seen in mechanical properties. Changes in interfacial shear strength and the matrix strength with temperature lead to different failure modes at higher temperatures. These failure modes also allow toughening at higher temperatures. High temperature mechanical behaviour of an uncoated SiC-SiC composite material Gomina, M., Fourvel, P. and Rouillon, M.-H. Journal o f Materials Science Vo126 No 7 (1991) pp 1891-1898 Three-point bend tests have been carried out on a CVI-I~SiC matrix reinforced with Nicalon SiC fibres from 22°C to 1200°C. Two failure modes were observed: below 700°C failure is controlled by the fibre/matrix interface with considerable fibre pull-out, while above this temperature brittle failure took over. Mechanical properties of a zircon matrix composite reinforced with silicon carbide whiskers and filaments Singh, R.N. Journal o f Materials Science Vol 26 No 7 (1991) pp 1839-1846 Silicon carbide whiskers have been used to reinforce a zircon matrix already reinforced
CARBON MA TRICES Failure analysis and damage initiation in carbon-carbon composite materials under three-point bending Copp, P.D., Dendis, J.C. and Mall, S. Journal o f Composite Materials Vol 25 No 5 (1991) pp 593-608 This paper investigates the damage and resulting failure modes caused in carbon/ carbon composites by the contact stresses caused by attaching them to other components with fasteners. Fastening is simulated using the three-point bend test, which the simplest contact arrangement available. Damage initiation and failure mechanisms are studied for woven uncoated carbon/ carbon composites in long and short beam geometries.
CERAMIC FIBRES Composition-microstruct ure-property relationships in ceramic monofilaments resulting from the pyrolysis of a polycarbosilane precursor at 800 to 1400°C Bouillon, E., Mocaer, D., Villencuve, J.F., Pailler, R., Naslain, R., Monthioux, M., Oberlin, A., Guimon, C. and Pfister, G. Journal o f Materials Science Vol 26 No 6 (1991) pp 1517-1530 Monofilaments have been drawn from a polycarbosilane melt, cross-linked with oxygen and pyrolysed between 800°C and 1400~C. The processes taking place during pyrolysis have been examined and the resulting fibres extensively characterized. The fibres are composed of amorphous material that is stable up to about 1100~C. Above this temperature a crystalline state evolves, resulting in a drop in the tensile strength. The mechanisms involved in pyrolysis and the amorphous to crystalline transition are discussed.
472
CVD Mo, W and Cr oxycarbide, carbide and silicide coatings on SiC yarn Kmetz, M., Tan, B.J., Willis, W., Suib, S. and Galasso, F.S. Journal o f Materials Science Vol26 No 8 (1991) pp 2107-2110 The possibility of coating silicon carbide fibres using Mo, W and Cr carbonyl systems has been explored. Fibres were successfully coated with the oxycarbides without degradation. Heat treatment in nitrogen converted the oxycarbides to metals and further heat treatment in SiCI 4 produced silicide coatings. A longer coating time was used to form a SiC/tungsten oxycarbide composite which had a tensile strength of 193 MPa. Silsesquioxane-drived ceramic fibres Hurwitz, F.I., Farmer, S.C., Tcrepka, F.M. and Leonhardt, T.A. Journal o f Materials Science Vo126 No 5 (1991) pp 1247-1252 Fibres have been drawn from blends of commercially available siisesquioxane polymers, before prolysing in an argon atmosphere to yield an Si-C-O fibre. The blends have been characterized using differential scanning calorimetry and thermogravimetric analysis. The structure and chemistry of the fibres has been examined by SEM, TEM and microanalysis. The microstructure was rather inhomogeneous on the scale of a few microns, which is attributed to the low miscibility of the polymers used. On the namometre scale phase-separated microstructures were observed. Depending on the blend of polymers used and the pyrolysis conditions, both silicon oxycarbide and SiC fibres have been produced. Testing E-glass bundles using acoustic emission Cowking, A., Attou, A., Siddiqui, A.M., Sweet, M.A.S. and Hill, R. Journal o f Materials Science Vo126 No 5 (1991) pp 1301-1310 Acoustic emission has been used to follow individual fibre failures in a lubricated bundle of E-glass fibres. By this method it was found possible to generate the fracture stress distribution of the fibres in the bundle. While these results may be fitted with Weibull statistics, the method described does not rely on this and could be applied where the distribution does not fit such an expression or where failure is not perfectly elastic.
CERAMIC MA TRICES Determination of fibre-matrix interfacial properties in ceramic-matrix composites by a fibre push-out technique Singh, R.N. and Sutcu, M. Journal o f Materials Science I/ol26 No 9 (1991) pp 2547-2556 A concentric cylinder model is used to interpret indenter load/displacement curves for fibre push-out tests in ceramic-matrix composites. The model assumes that the interface is partially bonded and partially frictionally coupled. A change of slope of the loading curve is shown to correspond to bonding at
COMPOSITES. NOVEMBER 1991
the interface, whereas little change is predicted for a frictionally coupled interface. This model provides a method for determining the interfacial debond energy and interfacial shear strength from fibre push-out tests. The predictions of this model are compared with test results on Zircon/SiC composites uniaxially reinforced with uncoated or BN-coated SiC microfilaments. The results suggest that the fibre/matrix interfaces of these composites are frictionally coupled. Discrete failure mode detection in a woven SiC cloth reinforced glass composite Krynicki, J.W., Green, R.E. and Nagle, D.C. Journal o f Materials Science Vo126 No 8 (1991) pp 2184-2188 A single layer of SiC cloth has been used to reinforce a borosilicate glass. The fracture in three-point bend of this material has then been observed optically, to try to explain anomalies in the load/deflection curves. Acoustic emission was also used to monitor the fracture process. The failure mode observed by these techniques was of a first crack starting on the tensile face and propagating to the fibre layer; at this point a second crack initiated on the opposite side of the fibre layer which is eventually put in tension as fibre pull-out occurs. Elevated temperature mechanical properties of continuous metallic glass ribbon-reinforced glass-ceramic matrix composites Vaidya, R.U. and Subramanian, K.N. Journal o f Materials Science Vol 26 No 5 (1991) pp 1391-1394 Three-point bend tests have been carried out at temperatures up to 500°C on samples of a glass-ceramic matrix composite reinforced with a small volume fraction of continuous metallic ribbon. At room temperature significant improvements are seen in mechanical properties. Changes in interfacial shear strength and the matrix strength with temperature lead to different failure modes at higher temperatures. These failure modes also allow toughening at higher temperatures. High temperature mechanical behaviour of an uncoated SiC-SiC composite material Gomina, M., Fourvel, P. and Rouillon, M.-H. Journal o f Materials Science Vo126 No 7 (1991) pp 1891-1898 Three-point bend tests have been carried out on a CVI-I~SiC matrix reinforced with Nicalon SiC fibres from 22°C to 1200°C. Two failure modes were observed: below 700°C failure is controlled by the fibre/matrix interface with considerable fibre pull-out, while above this temperature brittle failure took over. Mechanical properties of a zircon matrix composite reinforced with silicon carbide whiskers and filaments Singh, R.N. Journal o f Materials Science Vol 26 No 7 (1991) pp 1839-1846 Silicon carbide whiskers have been used to reinforce a zircon matrix already reinforced