wwceramics. org/ACT Infuence of Interface Characteristics on the Mechanical Properties fiber fiber fiber Fig. 6. Scanning electron micrographs showing the surface of pullout fibers in( a) a Hi-Nicalon S/SiC minicomposite,()an SA3/SiC incomposite, and cross-sections of (c) an Hi-Nicalon S/Si C minicomposite, and (d)an SA3/SiC minicomposite. that high thermally induced residual stresses should not tends to weaken the interphase opening strength be expected which is a favorable feature in terms of crack devia- Thermally induced residual stresses were deter- tion. Similar trends were obtain multilayered mined considering a single fber and concentrical interphases cylinders of interphase and matrix. Figure 10 shows Thus, as expected, because of their similarity, the that comparable stress states were obtained for th differences in the mechanical behaviors of SA3/SiC and Hi-Nicalon S/SiC and SA3/SiC, involving tensile stres- Hi-Nicalon S/SiC minicomposites cannot be attributed ses in fibers and interphases, and compressive stresses to the contribution of thermally induced residual stress in the matrix. The presence of tensile radial stresses states to the fiber/matrix bond. (a) Fig. 7. Atomic force microscopic images of the surface of (a)Hi-NicalonS fber and (b) SA3 fiber.that high thermally induced residual stresses should not be expected. Thermally induced residual stresses were deter￾mined considering a single fiber and concentrical cylinders of interphase and matrix.27 Figure 10 shows that comparable stress states were obtained for the Hi-NicalonS/SiC and SA3/SiC, involving tensile stres￾ses in fibers and interphases, and compressive stresses in the matrix. The presence of tensile radial stresses tends to weaken the interphase opening strength, which is a favorable feature in terms of crack devia￾tion. Similar trends were obtained for multilayered interphases. Thus, as expected, because of their similarity, the differences in the mechanical behaviors of SA3/SiC and Hi-NicalonS/SiC minicomposites cannot be attributed to the contribution of thermally induced residual stress states to the fiber/matrix bond. Fig. 6. Scanning electron micrographs showing the surface of pullout fibers in (a) a Hi-NicalonS/SiC minicomposite, (b) an SA3/SiC minicomposite, and cross-sections of (c) an Hi-NicalonS/SiC minicomposite, and (d) an SA3/SiC minicomposite. Fig. 7. Atomic force microscopic images of the surface of (a) Hi-NicalonS fiber and (b) SA3 fiber. www.ceramics.org/ACT Influence of Interface Characteristics on the Mechanical Properties 299