RH. Jones et al. I Journal of Nuclear Materials 307-311(2002)1057-1072 600 500 500 Unirradiated (5073 75 MPa) E苏 00 Unirradiated (267+ 70 MPa) 200 1.1dpa【216"C) 1.1dpa(385°c) 200 10D 00010020030.04005006 00010D20.B0.040.050.06 Cross Head Displacement(cm) Cross Head Displacement (cm) ated(514土224Pa) 1.1dpa(260°c) 0010D20B3004t.D5.D6 Fig. 8. Bend-displacement curves for SiC/SiC with(a) pyrolytic C,(b)multiplayer, and (c) porous interfaces. studies have shown how Ker depends upon constituent For fiber-to-matrix conductivity ratios(r)less than fiber and matrix thermal conductivity values, and their 10(r< 10) and for fiber volume fractions, ()<0.5, the volume fractions and distributions [30-33. However, Hasselman-Johnson(H-J) model predictions given by many experimental measurements have indicated that Eq (1) deviate from numerical FEM results by less than interfaces between fibers and matrices in a composite 5%. By Eq. (I), for dispersed fibers in a matrix the ef- introduce a thermal barrier that may reduce Keff [34-37. fective transverse thermal conductivity(Ker)is primarily Furthermore, Kefr may be altered by physical changes of controlled by the thermal conductivity of the continuous the interface and even the surrounding atmosphere. As matrix phase(Km)and the interfacial conductance(h).A with mechanical behavior, to attain desired thermal simple thermal barrier model was introduced to describ behavior of SicSiC proper attention needs to be given h and the gaseous and direct contact components fgh to the design of the interphase and the control of and fahd, respectively ) Values of h determined by ec interfacial thermal effects. Classical composite models (2)for a uniaxial Hi-Nicalon fiber/amorphous SiC recently have been updated to include the effect of in- matrix composite in vacuum, argon and helium com- terfacial thermal barriers [38]. Interfacial thermal bar- pared favorably with values estimated by the simple riers are quantitatively characterized by a value called thermal barrier model. reasonable agreement between the interfacial conductance, which includes the effect of numerical FEM and experimental results with H-J imperfect matching of surfaces at an interface as well as model predictions suggest that Kefr for a Sicr/Sic com- the effect of interfacial gaps brought about by debonding posite with fiber volume fractions f<0.4 and with of the fiber from the matrix or microcracking within the simple unidirectional or cross-ply fiber architecture are fiber coating [38] well described by eq (1) belowstudies have shown how Keff depends upon constituent fiber and matrix thermal conductivity values, and their volume fractions and distributions [30–33]. However, many experimental measurements have indicated that interfaces between fibers and matrices in a composite introduce a thermal barrier that may reduce Keff [34–37]. Furthermore, Keff may be altered by physical changes of the interface and even the surrounding atmosphere. As with mechanical behavior, to attain desired thermal behavior of SiCf /SiC proper attention needs to be given to the design of the interphase and the control of interfacial thermal effects. Classical composite models recently have been updated to include the effect of in￾terfacial thermal barriers [38]. Interfacial thermal bar￾riers are quantitatively characterized by a value called the interfacial conductance, which includes the effect of imperfect matching of surfaces at an interface as well as the effect of interfacial gaps brought about by debonding of the fiber from the matrix or microcracking within the fiber coating [38]. For fiber-to-matrix conductivity ratios (r) less than 10 (r < 10) and for fiber volume fractions, ðf Þ 6 0:5, the Hasselman–Johnson (H–J) model predictions given by Eq. (1) deviate from numerical FEM results by less than 5%. By Eq. (1), for dispersed fibers in a matrix the ef￾fective transverse thermal conductivity (Keff ) is primarily controlled by the thermal conductivity of the continuous matrix phase (Km) and the interfacial conductance (h). A simple thermal barrier model was introduced to describe h
and the gaseous and direct contact components (fghg and fdhd, respectively). Values of h determined by Eq. (2) for a uniaxial Hi-Nicalone fiber/amorphous SiC matrix composite in vacuum, argon and helium com￾pared favorably with values estimated by the simple thermal barrier model. Reasonable agreement between numerical FEM and experimental results with H–J model predictions suggest that Keff for a SiCf /SiC com￾posite with fiber volume fractions f 6 0:4 and with simple unidirectional or cross-ply fiber architecture are well described by Eq. (1) below: Fig. 8. Bend-displacement curves for SiCf /SiC with (a) pyrolytic C, (b) multiplayer, and (c) porous interfaces. 1064 R.H. Jones et al. / Journal of Nuclear Materials 307–311 (2002) 1057–1072