The Experimental Equipment And Mechanical Properties Analysis Of C/SiC Composites Under The Service Temperature

Continuous carbon fiber reinforced SiC matrix composites?C/SiC? have been applied widely in astronautic and aeronautic fields for its excellent properties including high temperature resistance, desirable corrosion resistance, high oxidation resistance, high wear resistance and low density. Therefore, investigations on the properties of C/SiC composites have attracted much more attentions in recent years, especially mechanical properties under high temperatures. However, it is a huge challenge to characterize the performances of C/SiC materials by using traditional methods under high-temperature service environments. Therefore, we proposed a new method and experimental system to characterize the properties of the C/SiC composites at high temperatures on the basis of non-contact digital image technology?DIC? technique in this paper. Fracture characteristics and crack extension resistance curves?R-curve? of C/SiC samples were systematically studied in room temperature. Bending properties of C/SiC samples were tested within a range from 1000 °C to 1600 °C. Tensile characteristics of C/SiC samples were investigated within a range from room temperature to 1000 °C. The main research contents are summarized as follows,Firstly, a set of high temperature material mechanical performance test system technique was designed and developed independently, including testing machine, high temperature furnace, three-dimensional digital image correlation deformation measurement system, lighting system and infrared filter system. The mechanical properties within a range from room temperature to 1600 °C were characterized by using self-developed high temperature resistant speckle methods.Secondly, fracture strength and fracture toughness of C/SiC composites were evaluated by single edged notched beam?SENB? at room temperature. The R-curve characteristics of C/SiC composites were discussed under cyclic loads. The results show that the fracture toughness and fracture strength of C/SiC composites are 7.81 ± 0.12 MPa?m^1/2 and 223.23 ± 3.5 MPa, respectively. With the propagation of cracks, the stress intensity factor increases gradually from 4.68 MPa?m^1/2 to 16.83 MPa?m^1/2 during the R-curve tests.Thirdly, fracture strength and fracture toughness of C/SiC composites were studied within a range from 1000 °C to 1600 °C, respectively. The results show that fracture strength of C/SiC composite decreases from 96.97 MPa to 29.73 MPa with increasing of experimental temperatures, while the fracture toughness display similar evolution, which varies from 8.55 MPa?m^1/2 to 2.26 MPa?m^1/2. It is interesting to find that the fracture mode of C/SiC composites gradually transformed from brittle to ductile before and after about 1300 °C.Finally, the elastic modulus and tensile strength of C/SiC composites were estimated by tensile tests from room temperature to 1000 °C. It is found that both elastic modulus and tensile strength of C/SiC composites gradually increase from 62.7 GPa and 209.8 MPa at room temperature to 91.3 GPa and 221.6 GPa at 600 oC, respectively. And then they decreases from 91.3 GPa to 31.6 GPa, from 221.6 MPa to 131.3 MPa after 600 oC, respectively.