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A.A. Kolchin et al. /Composites Science and Technology 61(2001)1079-1082 l081 h= about 5 mm Q ch=0.37-042 Fig. 2. Composite specimens to measure (a) bending strength and (b)critical stress-intensity factor Sintering time 1 h 12 ●3h E350 30 13601370138013901400 Sintering temperature /C Fibre volume fraction Fig3. Bending strength of alumina matrix versus sintering tempera- Fig. 5. Critical stress intensity factor of sapphire-fibre/alumina-matrix ture. Sintering was done under a pressure of 70 MPa composite versus fibre volume fraction. Sintering regime is 1400.C 70 MPa-3 h c450 400 Sintering time o 1 h 350 v300 8250 0.000.020.040.060.080.100.12 Fibre volume fraction 100μ m Fig. 4. Bending strength of sapphire-fibre/alumina-matrix composite rsus fibre volume fraction. Sintering temperature is 1400.C. Fig. 6. The failure surface of a composite specimen To choose the fabrication parameters for making composite specimen, a number of matrix specimens 3. Discussion and conclusions were made and tested, Fig 3, and the temperature-time conditions were determined as 1400C for 3 h. Depen Two obvious conclusions can be drawn First. rein- dencies of the strength and fracture toughness on the forcing the alumina matrix with ICM sapphire fibres fibre volume fraction are presented in Figs. 4 and 5. does not essentially change the material strength that - - , - 4, 9 C )>''3 - 9 : . - , - , # - 4, > B # 4 . -, @3 , , 4, & 3 67 , , 67 . - 4, 9 5, , - # , . , - F' E 4, > 5, , - . . # # - , )>''3 4, B 3 - - . . # # - , , )>''3 M F' E M 9 4, * - - - %% ! % ) & * + , -- . -/01 -2 )'$)