M. Kotani et al. /Composites Science and Technology 62(2002)2179-2188 Fig. 11. SEM micrographs of as-consolidated bodies at the heating rates of (a)600,(b)30, and(c)10 K/h. could be seen more cracks as the heating rate increased. This feature should be related with gas evolution rate during consolidation and provide main influence on 700 1 MPa relative density. Since these kinds of morphologies would remain after multiple densification processing, ■10MPa heating condition during consolidation should be also appropriately selected to control these negative influences Fig. 12 exhibits average flexural strengths of the composites, which were summarized as the functions of (a) curing temperature and (b) pressure. The strengths were distributed between 200 and 700 MPa and closely dependent on curing temperature, as shown in (a) Curing temperature /K Those became higher as curing temperature was low ered. The composites, which were obtained from highly 583K (623, 10), didnt show remarkable high strength. This implied that densification of a consolidated body did not lead to apparent mechanical improvement directly. for pressure, no representative depende shown in(b) Fig. 13 represents flexural strengths of the composites consolidated at various heating rates. Unified tendency for all composites was not seen. The effect of crack dis- tribution that was shown in Fig. Il on mechanical per formance was not be revealed. On the whole. the composites fabricated at lower curing temperature Pressure/MPa showed higher strength. And strengths became more Fig. 12. Flexural strengths of the composites fabricated under various constant as curing temperature increased. These fea- conditions of (a)curing temperature and (b)pressure. tures were also shown in Fig. 12. According to these results, only curing temperature hardening of the slurry as curing temperature increased was approved to be influential factor for flexural Therefore, it was found that the flexural strength had strength. For this factor, any change in microstructure close dependence on fiber volume fraction. In spite of would be brought about to affect flexural strength. concentrated effort on reducing porosity, remarkable Fig. 14 exhibited the relationship between fiber volume improvement of mechanical performance was not fraction and curing temperature of the consolidated achieved for r the comp osites obtained from highly com- bodies. Close dependence where fiber volume fraction pacted consolidated body. As for fracture behavior, was linearly decreased along with curing temperature almost all composites tested showed non-catastrophic was shown. It was considered that compacting efficiency feature, even though no interfacial layer was presently of a green body by pressurization would decline due to introduced. Since no big difference was presented incould be seen more cracks as the heating rate increased. This feature should be related with gas evolution rate during consolidation and provide main influence on relative density. Since these kinds of morphologies would remain after multiple densification processing, heating condition during consolidation should be also appropriately selected to control these negative influences. 3.2.3. Flexural test Fig. 12 exhibits average flexural strengths of the composites, which were summarized as the functions of (a) curing temperature and (b) pressure. The strengths were distributed between 200 and 700 MPa and closely dependent on curing temperature, as shown in (a). Those became higher as curing temperature was low￾ered. The composites, which were obtained from highly consolidated bodies in the conditions of (603, 5) and (623, 10), didn’t show remarkable high strength. This implied that densification of a consolidated body did not lead to apparent mechanical improvement directly. As for pressure, no representative dependence was shown in (b). Fig. 13 represents flexural strengths of the composites consolidated at various heating rates. Unified tendency for all composites was not seen. The effect of crack dis￾tribution that was shown in Fig. 11 on mechanical per￾formance was not be revealed. On the whole, the composites fabricated at lower curing temperature showed higher strength. And strengths became more constant as curing temperature increased. These fea￾tures were also shown in Fig. 12. According to these results, only curing temperature was approved to be influential factor for flexural strength. For this factor, any change in microstructure would be brought about to affect flexural strength. Fig. 14 exhibited the relationship between fiber volume fraction and curing temperature of the consolidated bodies. Close dependence where fiber volume fraction was linearly decreased along with curing temperature was shown. It was considered that compacting efficiency of a green body by pressurization would decline due to hardening of the slurry as curing temperature increased. Therefore, it was found that the flexural strength had close dependence on fiber volume fraction. In spite of concentrated effort on reducing porosity, remarkable improvement of mechanical performance was not achieved for the composites obtained from highly com￾pacted consolidated body. As for fracture behavior, almost all composites tested showed non-catastrophic feature, even though no interfacial layer was presently introduced. Since no big difference was presented in Fig. 11. SEM micrographs of as-consolidated bodies at the heating rates of (a) 600, (b) 30, and (c) 10 K/h. Fig. 12. Flexural strengths of the composites fabricated under various conditions of (a) curing temperature and (b) pressure. 2186 M. Kotani et al. / Composites Science and Technology 62 (2002) 2179–2188