Journal of the American Ceramie Society-Morscher er al Vol 87. No. 1 2014 Fib BN Fig. 4. FESEM images of fracture surfaces of SYL- iBN composites showing outside debonding (a, b) and inside debonding (e, d). higher than the stresses for matrix cracks to penetrate the load- contact. the thinner areas of Bn were oxidized and fiber-to-fiber bearing fibers (determined from the onset of hysteresis loop fusion occurred for rupture times greater than 80 h. There were activity,-175 MPa for/= 0.2 composites used in this study ) In several regions of significant fiber pullout throughout the cross other words, the SYL-iBN composites are significantly cracked at section of the fracture surface. the stress-rupture conditions of this study, even for specimens that did not fail after long periods of time. L A few specimens(SYL and SYL-iBN) were precracked at room mperature and compared with the rupture behavior of pristine Examination of the rupture specimen fracture surfaces con- specimens from the same panel (Fig. 8). It was evident that firmed the survival of most of the BN around the fibers in the inside-debonding SYL composites with nominally good matrix crack even though significant oxidation had occurred in the properties were significantly poorer in rupture behavior with matrix crack (Fig. 7). However, at regions of near fiber-to-fiber precracking as has been observed in another study. On the other 6001 77 GPa 50050 f=0.18 f 400 Strain. f=0.17 = Change in slope at 70 MPa not associated with occurrence of ae 0.1 030 Strain, Fig. 5. Room-temperature tensile stress-strain curves for a number of outside-debonding composites with difterent fiber volume tractions