w. Xiaojun et al./ Composites Science and Technology 66(2006)993-1000 z8E5品3 of microcracks at front z巴E quantity of microcracks at the side near notch - quantity of microcracks at front H quantity of microcracks at the far from notch side far from the notch Fig. 6. Amount of micro-cracks as a function of time for D-C/SiC tensile creep specimen at 1500C and 95 MPa in vacuum. (a)on the top surface of the specimen and (b) on the lateral side of the specimen 0.5h h Fig. 7. The crack width variation with creeping time in the near notch area and on the lateral side of the 2D-C/Sic tensile creep specimen at 1500C and the near notch areas on the top surface of the specimen, U2 10 is for near notch areas on the lateral side of the specimen D3 is for the areas far from the notch on the top surface, and D4 is for the areas far from the notch on the lateral side sur- face. Notice that the growth rate of micro-cracks decreases 2 constantly. The fastest growth stage of micro-cracks is 10203040 within 10 h: the growth rate of the micro-cracks of the near 50 60 notch area has been faster than that for the far notch area within 2 h, in contrast the growth rate of micro-cracks at Fig 8. Evolution of crack width as a function of time for a notched 2D.c/ the area far from notch has been faster than that of the Sic tensile creep specimen at 1500C and 95 MPa in vacuum. near notch area in the period of 2-10 hthe near notch areas on the top surface of the specimen, v2 is for near notch areas on the lateral side of the specimen, v3 is for the areas far from the notch on the top surface, and v4 is for the areas far from the notch on the lateral side sur￾face. Notice that the growth rate of micro-cracks decreases constantly. The fastest growth stage of micro-cracks is within 10 h: the growth rate of the micro-cracks of the near notch area has been faster than that for the far notch area within 2 h, in contrast the growth rate of micro-cracks at the area far from notch has been faster than that of the near notch area in the period of 2–10 h. 0 0 10 20 30 40 50 60 quantity of microcracks at front near notch quantity of microcracks at front far from notch 0 10 20 30 40 50 0 20 40 Quantity of microcracks/ N quantity of microcracks at the side near notch quantity of microcracks at the side far from the notch 60 t (h) t (h) 10 20 30 40 50 60 Quantity of microcracks/ N a b Fig. 6. Amount of micro-cracks as a function of time for notched 2D-C/SiC tensile creep specimen at 1500 C and 95 MPa in vacuum, (a) on the top surface of the specimen and (b) on the lateral side of the specimen. Fig. 7. The crack width variation with creeping time in the near notch area and on the lateral side of the 2D-C/SiC tensile creep specimen at 1500 C and 95 MPa in vacuum, 50·. 0 2 4 6 8 10 12 0 10 20 30 40 50 60 t (h) Width of microcrack/ μm Fig. 8. Evolution of crack width as a function of time for a notched 2D-C/ SiC tensile creep specimen at 1500 C and 95 MPa in vacuum. W. Xiaojun et al. / Composites Science and Technology 66 (2006) 993–1000 997