S.T. Mileiko Current Opinion in Solid State and Materials Science 9(2005)219-229 120 n=7(calculated value) 100. 6 MPa The average fibre volume fraction is 0.26 Fig. 15. The calculated creep resistance of sapphire-fibre/alumina-matri composites at1200°C Fig 17. A load versus displacement curve obtained in testing YAG-fibre/ YAG-matrix specimen in 3-point bending. An increase in the slope of the curve is an effect caused by a testing machine and not by a special behaviour of a composite Hence, really high creep resistant composites of such types Experimental creep characteristics of sapphire-fibre/alumina-matrix com- are expected when YAG and mullite fibres are used in poly crystalline YAG and mullite matrices eep resistance(MPa) However, stability of macrostructures of both types A2005 very high temperatures for long time can hardly be obtained due to fibre/interphasematrix interaction and A2034 sintering the porous matrix. Hence, the authors' lab is A2053 now looking for new ways of organising non-brittle a2005 a2053 a2034 Fig. 16. Macrostructure of some sapphire/alumina specimensHence, really high creep resistant composites of such types are expected when YAG and mullite fibres are used in poly￾crystalline YAG and mullite matrices. However, stability of macrostructures of both types at very high temperatures for long time can hardly be obtained due to fibre/interphase/matrix interaction and sintering the porous matrix. Hence, the authors’ lab is now looking for new ways of organising non-brittle Table 2 Experimental creep characteristics of sapphire–fibre/alumina–matrix com￾posite specimens Specimen number n Creep resistance (MPa) A2005 6.01 94.9 A2007 5.60 77.8 A2034 5 64.3 A2053 2.85 38.1 Fig. 16. Macrostructure of some sapphire/alumina specimens. Fig. 15. The calculated creep resistance of sapphire–fibre/alumina–matrix composites at 1200 C. Fig. 17. A load versus displacement curve obtained in testing YAG–fibre/ YAG–matrix specimen in 3-point bending. An increase in the slope of the curve is an effect caused by a testing machine and not by a special behaviour of a composite. 228 S.T. Mileiko / Current Opinion in Solid State and Materials Science 9 (2005) 219–229