J Zhong et al. Journal of Materials Processing Technology 190(2007)358-362 36 room temperature 1300c wliw why strain, x 10 Fig 8. XRD pattern of matrix of the as-prepared composite Fig. 10. Stress vs strain curve for the as-prepared C/C/SiC composite. proportion of SiC. From this fact together with XRD pattern, it the as-prepared C/C/SiC composite. The stress-strain curve was suggested that the matrix formed by PlP did not consist of both at room temperature and 1300 C appeared ascending a mixture of carbon, SiC and Si3N4. It seemed to be a real com- zigzag, and that at room temperature exhibited more obvi- osite with Si-,C, and N-atoms as constituents. Consequently, ous non-linear behavior. As we known, the properties of the matrix was only considered as a Si-C-N composite, which material were determined by the structure. Zigzag character was C/C/SiC of the stress-strain curve probably is related to the lami nated structure of as-prepared composite showed in Fig. 4 3.3. Three-point-bending test When the crack propagated to the zone B, because of crack deflection, fiber debonding and pull-out, the crack propaga Three specimens were tested for room temperature and tion speed slowed down, and the stress increased with the 1300C, respectively. The test results dispersion was about increase of the strain until the crack crossed over the zone ten percent. Fig. 10 showed the typical failure behavior of B. With the increase of the stress, the damage in the co posite gradually increased. Damage implied the deformation in the macroscopic scale. When the damage accumulated to a certain extent, a pseudo-plasticity behavior appeared, in he way of zigzag stress-strain curves. It was obvious that the strain was very small both at room temperature and The stress-strain curve at 1300C displayed a typical fail ure process. The initial linear region AB corresponded to the elastic linear behavior of the material prior to any significant micro-failures. There was no damage generating in the com- posite at this stage. At an applied stress of point B there was a marked departure from linear behavior corresponding to trans- verse matrix cracking and to fiber/matrix debonding Region BC was believed to correspond to transverse crack multiplication 100um up to a saturation density. At an applied stress of point C fiber Electron Image 1 fractures and debonding which started before transverse matrix Spectrum 1 crack saturation continue until final failure [10]. The failure pro- cess at room temperature was similar to that of 1300C. But the flexural strength at room temperature was 121M was lower than 150 MPa at 1300C. The reason was that the residual thermal stress in the composite was partially relaxed at 1300°C. During the composite damaging process, there were several energy absorbed mechanisms which included matrix cracking, interface debonding, fiber pull-out and fiber fracture, these phe nomena did not occur in the monolithic ceramics. Owing to Full Scale 7411 cts Cursor. 0.000 damage process, the composite achieved more toughness com- Fig- 9. EDS pattern of matrix of the as-prepared composite paring with the matrix materiJ. Zhong et al. / Journal of Materials Processing Technology 190 (2007) 358–362 361 Fig. 8. XRD pattern of matrix of the as-prepared composite. proportion of SiC. From this fact together with XRD pattern, it was suggested that the matrix formed by PIP did not consist of a mixture of carbon, SiC and Si3N4. It seemed to be a real com￾posite with Si–, C–, and N-atoms as constituents. Consequently, the matrix was only considered as a Si–C–N composite, which was C/C/SiC. 3.3. Three-point-bending test Three specimens were tested for room temperature and 1300 ◦C, respectively. The test results dispersion was about ten percent. Fig. 10 showed the typical failure behavior of Fig. 9. EDS pattern of matrix of the as-prepared composite. Fig. 10. Stress vs. strain curve for the as-prepared C/C/SiC composite. the as-prepared C/C/SiC composite. The stress–strain curve both at room temperature and 1300 ◦C appeared ascending zigzag, and that at room temperature exhibited more obvi￾ous non-linear behavior. As we known, the properties of material were determined by the structure. Zigzag character of the stress–strain curve probably is related to the lami￾nated structure of as-prepared composite showed in Fig. 4. When the crack propagated to the zone B, because of crack deflection, fiber debonding and pull-out, the crack propaga￾tion speed slowed down, and the stress increased with the increase of the strain until the crack crossed over the zone B. With the increase of the stress, the damage in the com￾posite gradually increased. Damage implied the deformation in the macroscopic scale. When the damage accumulated to a certain extent, a pseudo-plasticity behavior appeared, in the way of zigzag stress–strain curves. It was obvious that the strain was very small both at room temperature and 1300 ◦C. The stress–strain curve at 1300 ◦C displayed a typical fail￾ure process. The initial linear region AB corresponded to the elastic linear behavior of the material prior to any significant micro-failures. There was no damage generating in the com￾posite at this stage. At an applied stress of point B there was a marked departure from linear behavior corresponding to trans￾verse matrix cracking and to fiber/matrix debonding. Region BC was believed to correspond to transverse crack multiplication up to a saturation density. At an applied stress of point C fiber fractures and debonding which started before transverse matrix crack saturation continue until final failure [10]. The failure pro￾cess at room temperature was similar to that of 1300 ◦C. But the flexural strength at room temperature was 121 MPa, which was lower than 150 MPa at 1300 ◦C. The reason was that the residual thermal stress in the composite was partially relaxed at 1300 ◦C. During the composite damaging process, there were several energy absorbed mechanisms which included matrix cracking, interface debonding, fiber pull-out and fiber fracture, these phe￾nomena did not occur in the monolithic ceramics. Owing to damage process, the composite achieved more toughness com￾paring with the matrix material