300 International Journal of Applied Ceramic Technolog-Sauder, Brusson and Lamon Vol. 7, No. 3, 2010 tert matrix fiber latr cracks Fig 8. Schematic diagrams showing interphase thickness(enyo) with respect to fiber surface amplitude: (a)eryc<h in the interface rack and (b)epyc>h in the interface crack, A=0 Discussion 一SA3fber -HS fber → SiC CVI matrix In summary, it appears that debonding occurred in both the Hi-NicalonS- and the SA3 fiber-reinforced minicomposites,at the fiber/interphase interface. A comparable opening strength can be logically expected in both systems. Thus, the differences in mechanical behavior can be attributed to postdebonding phenom ena in the interface cracks. It also appears that th surface roughness of fibers plays a major role in the postdebonding behavior of SA3/SiC minicomposites. t was much larger when compared with Hi-Nicalon S/Sic minicomposites, although no bond-strengthening treatment had been applied to fibers. Some SA3/SiC minicomposites exhibited strains as high as 0.6%, 200 400 600 800 1000 1200 which indicates that. as ed. fibers were not degraded during processing. Thermally induced resid ts of thermal expansion versus al stresses were found to be comparable, and they mperature for Hi-Nicalon S and SA3 fibers and CVI matrix(afier included radial tensile components that favor interface Michaux et al-)Discussion In summary, it appears that debonding occurred in both the Hi-NicalonS- and the SA3 fiber-reinforced minicomposites, at the fiber/interphase interface. A comparable opening strength can be logically expected in both systems. Thus, the differences in mechanical behavior can be attributed to postdebonding phenom￾ena in the interface cracks. It also appears that the surface roughness of fibers plays a major role in the postdebonding behavior of SA3/SiC minicomposites. t was much larger when compared with Hi-NicalonS/SiC minicomposites, although no bond-strengthening treatment had been applied to fibers. Some SA3/SiC minicomposites exhibited strains as high as 0.6%, which indicates that, as expected, fibers were not degraded during processing. Thermally induced resid￾ual stresses were found to be comparable, and they included radial tensile components that favor interface opening. Fig. 8. Schematic diagrams showing interphase thickness (ePyC) with respect to fiber surface roughness amplitude: (a) ePyCoh in the interface crack and (b) ePyC4h in the interface crack, A 5 0. Fig. 9. Plots of coefficients of thermal expansion versus temperature for Hi-NicalonS and SA3 fibers and CVI matrix (after Michaux et al.26). 300 International Journal of Applied Ceramic Technology—Sauder, Brusson and Lamon Vol. 7, No. 3, 2010