International ournal of Applied Ceramic Techmolog--Morscher and pujar Vol.6,No.2,2009 (a)0.351ZM-1121MPa (b)0.4 0.3//(rupture) 小2172MPa SA-1 172 MF SA-1 138 MP Syl-iBN-3 172 MF SA-1 103 MPa 0.15 詈015 Syl-2 103 MPa SA-1 138 MPa 1200C Creep 315C Creep 100 Time hours Fig. 6. Tensile creep total strain(elastic plus time-dependent)curves at(a)1200C and(b)1315C for diferent fiber-type MI composite The rupture results are plotted as composite stress some of the composite systems in their as-produced versus time at 1200.C and 1315 C in Fig. 7. Note that condition. This stress was calculated using Eq. (3)and a specimens that did not rupture are indicated by arrows. Ominimatrix stress of 95 MPa, as described earlier in Fig In general, the rupture resistance directly correlates to 5. The differences in the composite onset stresses for th the inherent creep and rupture resistance of the fibers, three different fiber composites are a result of differences with Syl-ibN composites being the most, and ZMI in the elastic modulus values for the fiber types as well as composites being the least, creep and rupture resistant. constituent volume fractions, especially fiber volume Also note that there were considerable differences in fi- differences between the composites. At 1200oC, the ber volume fraction between the different composite rupture data(Fig. 7a)show that the predicted onset systems studied, which in effect further accentuated the cracking stress correlates very well with the run-out con differences in the creep performance in these compos- ditions for all three composites systems. Because ites. The Syl- iBN composites, or the composites with the onset of matrix cracks and resultant environmental the most creep-resistant fiber, also had the highest fiber attack through the cracks is the most common mecha volume fractions and ZMI composites, or those with the nism leading to composite rupture under tensile creep, least creep-resistant fiber had the lowest fber volume. this suggests that the room-temperature criterion of (a) a Syl-iBN-3 1315G138M (b)240054N3 1801Hs2 10011315°cce Time. hr Fig.7. Tensile creep behavior of different MI composites at(a)1200C and(b)1315C. Each data point represents an individual specimen tix=95 MPa stress for designated composite pfailure or up to 500 h, followed by retained tensile property measurements at room temperature. The rupture results are plotted as composite stress versus time at 12001C and 13151C in Fig. 7. Note that specimens that did not rupture are indicated by arrows. In general, the rupture resistance directly correlates to the inherent creep and rupture resistance of the fibers, with Syl-iBN composites being the most, and ZMI composites being the least, creep and rupture resistant. Also note that there were considerable differences in fi- ber volume fraction between the different composite systems studied, which in effect further accentuated the differences in the creep performance in these compos￾ites. The Syl-iBN composites, or the composites with the most creep-resistant fiber, also had the highest fiber volume fractions and ZMI composites, or those with the least creep-resistant fiber had the lowest fiber volume. Figure 7 also shows the predicted composite stress for the onset of matrix cracking at room temperature for some of the composite systems in their as-produced condition. This stress was calculated using Eq. (3) and a sminimatrix stress of 95 MPa, as described earlier in Fig. 5. The differences in the composite onset stresses for the three different fiber composites are a result of differences in the elastic modulus values for the fiber types as well as constituent volume fractions, especially fiber volume differences between the composites. At 12001C, the rupture data (Fig. 7a) show that the predicted onset cracking stress correlates very well with the run-out con￾ditions for all three composites systems. Because the onset of matrix cracks and resultant environmental attack through the cracks is the most common mecha￾nism leading to composite rupture under tensile creep, this suggests that the room-temperature criterion of 0 0.05 0.1 0.15 0.2 0.25 0.3 (a) 0.35 (b) 0 20 40 60 80 100 120 0 20 40 60 80 100 120 Time, hours Total Strain, % SA-1 138 MPa 1200°C Creep SA-3 155 MPa SA-1 172 MPa (rupture) Syl-iBN -3 209 MPa (rupture) Syl-iBN-3 172 MPa ZMI-1 121 MPa (rupture) ZMI-1 103 MPa 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 Time, hours Total Strain, % 1315°C Creep Syl-2 103 MPa Syl-2 138 MPa Syl-2 172 MPa (rupture) SA-1 138 MPa (rupture) SA-1 103 MPa Fig. 6. Tensile creep total strain (elastic plus time-dependent) curves at (a) 12001C and (b) 13151C for different fiber-type MI composites. 80 100 120 140 160 180 200 220 (a) 240 (b) 0.1 1 10 100 1000 Time, hr Composite Stress, MPa Syl-iBN-3 Syl-iBN-1 SA-3 ZMI-1 ZMI-2 Syl-iBN-3 Pre-crept at 1315C; 138 Mpa Crept to failure at 1200C 1200°C Creep Syl-3 SA-3 ZMI-1 80 100 120 140 160 180 200 220 240 1 10 100 1000 Time, hr Composite Stress, MPa Syl-iBN-3 Syl-iBN-2 Syl-iBN-1 SA-1 SA-2 SA-3 HNS-2 [5] 1315°C Creep Syl-3 SA-3 HNS-2 Fig. 7. Tensile creep behavior of different MI composites at (a) 12001C and (b) 13151C. Each data point represents an individual specimen. Dashed lines represent the sminimatrix 5 95 MPa stress for designated composite panel. 158 International Journal of Applied Ceramic Technology—Morscher and Pujar Vol. 6, No. 2, 2009