S.M. Dong et al. Ceramics International 28(2002)899-905 Fig 3. Comparison of the microstructural evolution of the PIMP composites:(a),(b)TSA/SiC;(c).(d) TSA/C/SiC. The microstructure of the composites at a higher 3. 2. Physical and mechanical properties magnification is shown in Fig. 3b and d. Some micro- cracks can be observed around the fibers. Even though Table 2 lists some physical and mechanical properties large amounts of inter-bundle and intra-bundle matrix of the composites. Bulk density of TSA SiC composite were effectively formed in TSA/C/SiC composite, the is relatively high(2.51 g/cm)compared to that(2.30 g/ intra-bundle matrix seems to be loosely consolidated. cm) for TSA/C/SiC composite In composite TSA/SiC. This feature could be distinguished from the inter-bun- as discussed in the previous section, intra-bundle matrix dle matrix areas was gradually grown around the fibers when increasing TEM observation of the matrix from AHPCS pre- the number of impregnation cycles. After eight cycles cursor is shown in Fig. 4. It can be evidenced from the PIMP process, polymer derived matrix was formed in SAD-pattern that the matrix is completely amorphous, the intra-bundle and inter-bundle areas. Although some probably due to the very short pyrolysis time and low big pores inevitably existed, the density of TSA/SiC pyrolysis temperature(around 1100C) could still reach 2.51 g/cm. In the TSA/C/SiC compo site, the formation of relatively loose microstructure with the inclusion of Sic particulates and the les efficient impregnation cycles might explain the lower Fiber density. Bending test results indicate that higher strength Interface could be obtained for the composite with higher density (TSA/SiC). The average strength of this composite is over 400 MPa. While for the composites with lower density, strength is at a lower level Matrix To better understand the interaction between fibers and matrix, push-out and push-back tests were con- ducted on each composite. Typical curves are shown in 500n Fig. 5a. Protruding fiber is also demonstrated as an example in Fig 5b. In TSA/C/SiC, debonding mainly Fig. 4. TEM image and SAD-pattern (inset) of the composite TSA/ occurred in the fiber/carbon interface during push-out Sic showing the formation of non-crystallized matrix. test. In Fig. 5, Po represents the push-out load, whichThe microstructure of the composites at a higher magnification is shown in Fig. 3b and d. Some micro￾cracks can be observed around the fibers. Even though large amounts of inter-bundle and intra-bundle matrix were effectively formed in TSA/C/SiC composite,the intra-bundle matrix seems to be loosely consolidated. This feature could be distinguished from the inter-bun￾dle matrix areas. TEM observation of the matrix from AHPCS pre￾cursor is shown in Fig. 4. It can be evidenced from the SAD-pattern that the matrix is completely amorphous, probably due to the very short pyrolysis time and low pyrolysis temperature (around 1100
C). 3.2. Physical and mechanical properties Table 2 lists some physical and mechanical properties of the composites. Bulk density of TSA/SiC composite is relatively high (2.51 g/cm3 ) compared to that (2.30 g/ cm3 ) for TSA/C/SiC composite. In composite TSA/SiC, as discussed in the previous section,intra-bundle matrix was gradually grown around the fibers when increasing the number of impregnation cycles. After eight cycles PIMP process,polymer derived matrix was formed in the intra-bundle and inter-bundle areas. Although some big pores inevitably existed,the density of TSA/SiC could still reach 2.51 g/cm3 . In the TSA/C/SiC compo￾site,the formation of relatively loose microstructure with the inclusion of SiC particulates and the less efficient impregnation cycles might explain the lower density. Bending test results indicate that higher strength could be obtained for the composite with higher density (TSA/SiC). The average strength of this composite is over 400 MPa. While for the composites with lower density,strength is at a lower level. To better understand the interaction between fibers and matrix,push-out and push-back tests were con￾ducted on each composite. Typical curves are shown in Fig. 5a. Protruding fiber is also demonstrated as an example in Fig. 5b. In TSA/C/SiC,debonding mainly occurred in the fiber/carbon interface during push-out test. In Fig. 5, Po represents the push-out load,which Fig. 3. Comparison of the microstructural evolution of the PIMP composites: (a),(b) TSA/SiC; (c),(d) TSA/C/SiC. Fig. 4. TEM image and SAD-pattern (inset) of the composite TSA/ SiC showing the formation of non-crystallized matrix. 902 S.M. Dong et al. / Ceramics International 28 (2002) 899–905