K. Yoshida et al. / Composites Science and Technology 61(2001)1323-1329 oo-40vol% of fibers a 052vol% of fibers 三品E 1650 1750 Sintering temperature(C) Fig. 6. Maximum strength of the Sic/SiCr composites with about 40 and 52 vol %o of fibers fabricated by hot-pressing at various sintering (b) vol. of fibers was about twice as high as that of the composites with 40 vol. of fibers, and the SiC/SiCt composites hot-pressed at 1700C showed higher max imum strength than the composites hot-pressed at 1650 or 1750oC. In the case of the hot-pressing temperature of 1700 C, the composites with 40 and 52 vol. of fibers showed maximum strength of 120 and 240 MPa The present authors evaluated the mechanical prop erties of 2D-Sic/SiCr composites fabricated by the CVI and PIP methods, which were supplied as the round robin test materials [26]. The SiC/SiCr composites fab ricated by the CVi method (Vr=30%)had a maximum strength of 180-460 MPa, and the composites fabricated C by the Plp method (Ve=40%) showed a maximum strength of 20-50 MPa at room temperature. The max imum strength of the composites fabricated in this study was lower than the highest value of the composites fab- ricated by the Cvi method since the fiber strength of the composite fabricated by the CvI method should b higher than that of the composite fabricated by hot pressing mainly due to the difference in the processing temperature, i.e., processing temperature of hot-pressing is much higher than that of CVI. It has been reported that the tensile strength of Hi-Nicalon fiber after the thermal exposure in Ar atmosphere is maintained at around the original strength up to 1400C, however, it 50 um decreased gradually above 1400@C. The Hi-Nicalon fiber heat-treated at 1600 C retains approximately half Fig. 7. SEM micrographs of the fracture surface of the Sic/Sic the original strength [27-29 composites hot- pressed at(a)160°C,(b)1700°andc)1750° after SEM micrographs of the fracture surface of the Sic/ a three-point bending test at room temperature Fiber volume fraction SiCr composites with 40 and 52 vol% of fibers are was about voL% shown in Figs. 7 and 8, respectively. In the composite with 40 vol. of fibers, the length of The interfacial strength between fiber and matrix sig very short, whereas the composites with 52 vol. of nificantly affects the mechanical properties of fiber fibers showed large fiber pull-out. reinforced composites, and sintering temperature isvol.% of fibers was about twice as high as that of the composites with 40 vol.% of fibers, and the SiC/SiCf composites hot-pressed at 1700
C showed higher max￾imum strength than the composites hot-pressed at 1650 or 1750
C. In the case of the hot-pressing temperature of 1700
C, the composites with 40 and 52 vol.% of fibers showed maximum strength of 120 and 240 MPa, respectively. The present authors evaluated the mechanical prop￾erties of 2D-SiC/SiCf composites fabricated by the CVI and PIP methods, which were supplied as the round robin test materials [26]. The SiC/SiCf composites fab￾ricated by the CVI method (Vf=30%) had a maximum strength of 180–460 MPa, and the composites fabricated by the PIP method (Vf=40%) showed a maximum strength of 20–50 MPa at room temperature. The max￾imum strength of the composites fabricated in this study was lower than the highest value of the composites fab￾ricated by the CVI method since the fiber strength of the composite fabricated by the CVI method should be higher than that of the composite fabricated by hot￾pressing mainly due to the difference in the processing temperature, i.e., processing temperature of hot-pressing is much higher than that of CVI. It has been reported that the tensile strength of Hi-Nicalon fiber after the thermal exposure in Ar atmosphere is maintained at around the original strength up to 1400
C, however, it decreased gradually above 1400
C. The Hi-Nicalon fiber heat-treated at 1600
C retains approximately half the original strength [27–29]. SEM micrographs of the fracture surface of the SiC/ SiCf composites with 40 and 52 vol.% of fibers are shown in Figs. 7 and 8, respectively. In the composite with 40 vol.% of fibers, the length of fiber pull-out was very short, whereas the composites with 52 vol.% of fibers showed large fiber pull-out. The interfacial strength between fiber and matrix sig￾nificantly affects the mechanical properties of fiber￾reinforced composites, and sintering temperature is Fig. 6. Maximum strength of the SiC/SiCf composites with about 40 and 52 vol.% of fibers fabricated by hot-pressing at various sintering temperature. Fig. 7. SEM micrographs of the fracture surface of the SiC/SiCf composites hot-pressed at (a) 1650
C, (b) 1700
C and (c) 1750
C after a three-point bending test at room temperature. Fiber volume fraction was about 40 vol.%. K. Yoshida et al. / Composites Science and Technology 61 (2001) 1323–1329 1327