M. Kotani et al. / Composites Science and Technology 62(2002)2179-2188 号400 800 um Heating rate/Kh Fig. 13. Flexural strengths of the composites fabricated under various heating rate. n 10 MPa cog=o日 Fig. 15. Fracture surface of the composite consolidated in the condi- tions of (a)(583, 5). and(b)(603, 5) 600 fibers are hindered This feature suggested that fracture behavior of a composite was related with matrix micro- Curing temperature /K structure as well as fiber/matrix interfacial properties Fig. 14. Fiber volume fraction of each composite summarized as a And those factors might be related each other for frac- unction of curing temperature. ture behavior. It was considered that embrittlement occurred more easily as porosity of matrix was those stress-strain curves, those work- of fractures were decreased. Thus, main factors in mechanical perfor- nearly proportional to flexural strength. Therefore, it mance, such as fiber volume fraction, porosity and could be concluded that the consolidation condition interfacial property, should be syncetically controlled should be optimized to raise fiber volume fraction To acquire universal relationship among these factors is rather than decrease porosity for improving flexural essential for the final goal for establishing a process to strength of a composite, as far as the composite broke in fabricate high performance SiC/Sic composite for non-catastrophic fracture mode severe environments Basically, technical development to form homo- geneous matrix with smaller amount of defects is quite important for improving the performance and reliability 4. Conclusion of a composite. But the process optimization to reduce porosity didn,t lead to apparent improvement of flex- To fabricate a high performance SiC/SiC composite ural strength. Possible reason for this result was by PIP method, systematic process characterizations for appeared in fracture surface exhibited in Fig. 15. effective consolidation were performed with precise Although many pullout fibers of significant length inspection about the pyrolytic behavior of the polymeric shown in (a) were generally observed, those were precursor, polyvinylsilane. The following conclusions remarkably decreased in the composites obtained from were found highly consolidated bodies as represented in(b). In this case, toughening mechanism between fiber and matrix 1. Pvs was found to occur continuous thermoset would decline because mechanical independences of ting from viscous liquid to glassy solid betweenthose stress-strain curves, those work-of fractures were nearly proportional to flexural strength. Therefore, it could be concluded that the consolidation condition should be optimized to raise fiber volume fraction rather than decrease porosity for improving flexural strength of a composite, as far as the composite broke in non-catastrophic fracture mode. Basically, technical development to form homo￾geneous matrix with smaller amount of defects is quite important for improving the performance and reliability of a composite. But the process optimization to reduce porosity didn’t lead to apparent improvement of flex￾ural strength. Possible reason for this result was appeared in fracture surface exhibited in Fig. 15. Although many pullout fibers of significant length shown in (a) were generally observed, those were remarkably decreased in the composites obtained from highly consolidated bodies as represented in (b). In this case, toughening mechanism between fiber and matrix would decline because mechanical independences of fibers are hindered. This feature suggested that fracture behavior of a composite was related with matrix micro￾structure as well as fiber/matrix interfacial properties. And those factors might be related each other for frac￾ture behavior. It was considered that embrittlement occurred more easily as porosity of matrix was decreased. Thus, main factors in mechanical perfor￾mance, such as fiber volume fraction, porosity and interfacial property, should be syncetically controlled. To acquire universal relationship among these factors is essential for the final goal for establishing a process to fabricate high performance SiC/SiC composite for severe environments. 4. Conclusion To fabricate a high performance SiC/SiC composite by PIP method, systematic process characterizations for effective consolidation were performed with precise inspection about the pyrolytic behavior of the polymeric precursor, polyvinylsilane. The following conclusions were found. 1. PVS was found to occur continuous thermoset￾ting from viscous liquid to glassy solid between Fig. 13. Flexural strengths of the composites fabricated under various heating rate. Fig. 14. Fiber volume fraction of each composite summarized as a function of curing temperature. Fig. 15. Fracture surface of the composite consolidated in the condi￾tions of (a) (583, 5), and (b) (603, 5). M. Kotani et al. / Composites Science and Technology 62 (2002) 2179–2188 2187