HOUJun-iao et al/New Carbon Materials, 2009, 24(2): 173-177 Table 2 Life time of the 3D-C/SiC composites exposed at 600C 5 Qiao S R, Yang Zx, Han D, et al. Tensile creep damage and 900oC. and 1 300C in air at DE of 0. 1 and 0.29 creep mechanism of 3D-C/SiC composite[J] Journal of Materi- Damage time 600°C 900°C 1300°C als Engineering, 2004, 4: 34-36 D=0.1 3.3h 10.2h 6 Wu X J, Qiao S R, Hou J T, et al. Tensile creep damage of 2D-C/SiC composites evaluated using the fractal dimension and D=0.29 4.8h 11.3h >15h elastic modulus[ J]. New Carbon Materials 2006, 21(4): 321-325. [7 Wang L S, Xiong x, Xiao P, et al. Eflect of high temperature 4 Concluslons treatment on the fabrication and mechanical properties of The damage curves of the 3D-C/SiC composites exposed C/C-SiC composites[J]. New Carbon Materials, 2005, 20(3) at different temperatures in air can be divided into a sharp increasing stage(stage I)and a steady increasing stage(stage 18 Gerald C, Laurent G Stephane B. Development of damage in a II); stage I precedes stage Il. The damage evaluated by the 2D woven C/SiC composite under mechanical loading: I Me- elastic modulus decreases with temperature under the same chanical characterization[J]. Compos Sci TechnoL, 1996, 56 exposure temperature. The fracture strain and flexural strengt 1363-137 decrease to 2 5% and 44% of the initial value after 19 Lamouroux F, Camus Gi Kinetics and mechanisms of oxidation thermo-exposure at 1 300C for 15 h, whose degradations are of 2D woven C/SiC composites: I, Experimental approach[J].J considerably more obvious than that of the elastic modulus Am Ceram soc,1994,77(8):2049-2057 [10 Cheng L F, Xu Y D, Zhang L T, et al. Effect of heat treatment References on the thermal expansion of 2D and 3D C/SiC composites from room temperature to 1 400C[J]. Carbon, 2002, 41(8): 1666 [1 Krenkel W, Berndt F. C/C-SiC composites for space applica- 1670. tions and advanced friction systemsJ). Materials Science and [I1 Lamouroux F, Bourrat X, Naslain R Structure/oxidation behav Engineering A. 2005. 412 ior relationship in the carbonado 22] Schmidta S, Beyera S, Knabeb H, et al. Advanced ceramic ma- 2D-C/PyC/SiC composites[J]. Carbon, 1993, 31: 1273-1288. trix composite materials for current and future propulsion tech- [123 Cheng LE, Xu Y D, Zhang L T, et al. Effect of carbon interlayer nology applications[J]. Acta Astronautica, 2004, 55: 409-420 on oxidation behavior of C/SiC composites with a coating from 3] Ma J Q, Xu Y D, Zhang L T, et al. Preparation and mechanical room temperature to 1 500 C[]. Mater Sci Eng, A 2001, 300 219225 form[J]. Materials Letters, 2007, 61: 312-315 [ 13] Nagarajan A. Ultrasonic study of elasticity-porosity relationship 14 Qiao R, Han D, Li M, et al. Interaction between fatigue and in polystalline alumina J). J Appl Phys, 1971, 42: 3693-3696 creep and life prediction method of 3D-C/SiC(CV/Sih G C, Tu T, [14] Knudsen F P. Dependence of mechanical strength of brittle Wang Z D, editors. Structural Intergrity and Materials Ag- polycrystalline specimens on porosity and gain size]. J Am Ceram Soc,1959,42(8):376-387 University of Science and Technology Press, 2003: 129HOU Jun-tao et al. / New Carbon Materials, 2009, 24(2): 173–177 Table 2 Life time of the 3D-C/SiC composites exposed at 600 °C, 900 °C, and 1 300 °C in air at DE of 0.1 and 0.29 Damage time 600 °C 900 °C 1 300 °C DE=0.1 1.6 h 3.3 h 10.2 h DE=0.29 4.8 h 11.3 h >15 h 4 Conclusions The damage curves of the 3D- C/SiC composites exposed at different temperatures in air can be divided into a sharp increasing stage (stage I) and a steady increasing stage (stage II); stage I precedes stage II. The damage evaluated by the elastic modulus decreases with temperature under the same exposure temperature. The fracture strain and flexural strength decrease to 2.5% and 44% of the initial value after thermo-exposure at 1 300 °C for 15 h, whose degradations are considerably more obvious than that of the elastic modulus. References [1] Krenkel W, Berndt F. C/C–SiC composites for space applica￾tions and advanced friction systems[J]. Materials Science and Engineering A , 2005, 412 : 177-181. [2] Schmidta S, Beyera S, Knabeb H, et al. Advanced ceramic ma￾trix composite materials for current and future propulsion tech￾nology applications[J]. Acta Astronautica, 2004, 55: 409-420. [3] Ma J Q, Xu Y D, Zhang L T, et al. Preparation and mechanical properties of C/SiC composites with carbon fiberwoven per￾form[J]. Materials Letters, 2007, 61: 312-315. [4] Qiao S R, Han D, Li M, et al. Interaction between fatigue and creep and life prediction method of 3D-C/SiC[C]//Sih G C, Tu T, Wang Z D, editors. Structural Intergrity and Materials Ag￾ing-Fracture Mechanics and Applications. Shanghai: East China University of Science and Technology Press, 2003: 129. [5] Qiao S R, Yang Z X, Han D, et al. Tensile creep damage and creep mechanism of 3D-C/SiC composite[J]. Journal of Materi￾als Engineering, 2004, 4: 34-36. [6] Wu X J, Qiao S R, Hou J T, et al. Tensile creep damage of 2D-C/SiC composites evaluated using the fractal dimension and elastic modulus[J]. New Carbon Materials 2006, 21(4): 321-325. [7] Wang L S, Xiong X, Xiao P, et al. Effect of high temperature treatment on the fabrication and mechanical properties of C/C-SiC composites[J]. New Carbon Materials, 2005, 20(3): 245-249. [8] Gérald C, Laurent G, Stéphane B. Development of damage in a 2D woven C/SiC composite under mechanical loading: I. Me￾chanical characterization[J]. Compos Sci Technol, 1996, 56: 1363-1372. [9] Lamouroux F, Camus G. Kinetics and mechanisms of oxidation of 2D woven C/SiC composites: I, Experimental approach[J]. J Am Ceram Soc, 1994, 77(8): 2049-2057. [10] Cheng L F, Xu Y D, Zhang L T, et al. Effect of heat treatment on the thermal expansion of 2D and 3D C/SiC composites from room temperature to 1 400 °C[J]. Carbon, 2002, 41(8): 1666 -1670. [11] Lamouroux F, Bourrat X, Naslain R. Structure/oxidation behav￾ior relationship in the carbonaceous constituents of 2D-C/PyC/SiC composites[J]. Carbon, 1993, 31: 1273-1288. [12] Cheng L F, Xu Y D, Zhang L T, et al. Effect of carbon interlayer on oxidation behavior of C/SiC composites with a coating from room temperature to 1 500 ℃[J]. Mater Sci Eng , A 2001, 300: 219-225. [13] Nagarajan A. Ultrasonic study of elasticity-porosity relationship in polystalline alumina [J]. J Appl Phys, 1971, 42: 3693-3696. [14] Knudsen F P. Dependence of mechanical strength of brittle polycrystalline specimens on porosity and gain size[J]. J Am Ceram Soc, 1959, 42(8): 376-387