T Nozawa et aL/Journal of Nuclear Materials 384(2009)195-211 Material properties of low-density turbostratic carbon were of swelling saturates with increasing neutron dose(1 dpa). For summarized by Virgil'ev and Lebedev [35]. The density is x1.5 g/ irradiation temperatures less than 1000C, swelling is a strong cm. The elastic modulus ranged from 25 to 30 GPa. The coefficient function of temperature, decreasing with increasing temperature of thermal expansion of the low-density carbon is about I. The irradiation-induced change of Youngs modulus of SiC 2.8x 10/C. Neutron irradiation causes a significant shrinkage can be well-described by the Tersoff potential and the resulting when Tirr =140-750C, resulting in densification. With formation irradiation effects are well documented [4, 40. Because of lack of of a new system of micropores, the thermal expansivity of low- irradiation data on advanced SiC fibers, the post-irradiation prop density carbon reportedly decreases by irradiation. Because of lim- erties of Hi-Nicalon" Type-S fiber are presently assumed to be ited irradiation data available this study assumes no change of equivalent to those of CVD-SiC. However it is worth noting that re thermal expansivity by irradiation. The elastic modulus of low- cent data [41 identified some discrepancies in post-irradiation density carbon first decreases by irradiation and gradually in- properties of Sic fibers with CVD-Sic. The Poisson s ratio and the creases with increasing neutron fluence up to 1 x 10 n/cm. Be- thermal expansivity of Sic are assumed to be unchanged by yond this fluence, the elastic modulus seems to be saturated irradiation. (15% increase of the non-irradiated value Material properties of composites can be estimated by the rule High-crystallinity and high-purity Sic swells by irradiation with of mixtures, which is modified by Hashin for the transversely iso- the accumulation of radiation-induced defects and the magnitude tropic system[ 42. In this calculation for multilayer composites, (a)UD Hi-Nicalon Type-S/ PyC/CVI-SiC 400fNon-irradiated 1.8da3809 7.7dpa800°c 1.0dpa1000° (b)UD Hi-Nicalon Type-S/ ML/ CVI-Si 37dpa640°C Non-irradiated 77da800°C 42dpa1080°c 200 04 g stress-strain curves of as-received and neutron-irradiated unidirectional Hi-Nicalon Type-s/CVI-SiC composites with either(a)a Pyc monolayer or b)a pyc/sMaterial properties of low-density turbostratic carbon were summarized by Virgil’ev and Lebedev [35]. The density is 1.5 g/ cm3 . The elastic modulus ranged from 25 to 30 GPa. The coefficient of thermal expansion of the low-density carbon is about 2.8 106 /C. Neutron irradiation causes a significant shrinkage when Tirr = 140–750 C, resulting in densification. With formation of a new system of micropores, the thermal expansivity of low￾density carbon reportedly decreases by irradiation. Because of lim￾ited irradiation data available, this study assumes no change of thermal expansivity by irradiation. The elastic modulus of low￾density carbon first decreases by irradiation and gradually in￾creases with increasing neutron fluence up to 1 1021 n/cm3 . Be￾yond this fluence, the elastic modulus seems to be saturated (15% increase of the non-irradiated value). High-crystallinity and high-purity SiC swells by irradiation with the accumulation of radiation-induced defects and the magnitude of swelling saturates with increasing neutron dose (>1 dpa). For irradiation temperatures less than 1000 C, swelling is a strong function of temperature, decreasing with increasing temperature. [4]. The irradiation-induced change of Young’s modulus of SiC can be well-described by the Tersoff potential and the resulting irradiation effects are well documented [4,40]. Because of lack of irradiation data on advanced SiC fibers, the post-irradiation prop￾erties of Hi-NicalonTM Type-S fiber are presently assumed to be equivalent to those of CVD-SiC. However it is worth noting that re￾cent data [41] identified some discrepancies in post-irradiation properties of SiC fibers with CVD-SiC. The Poisson’s ratio and the thermal expansivity of SiC are assumed to be unchanged by irradiation. Material properties of composites can be estimated by the rule of mixtures, which is modified by Hashin for the transversely iso￾tropic system [42]. In this calculation for multilayer composites, Fig. 3. Typical tensile stress–strain curves of as-received and neutron-irradiated unidirectional Hi-NicalonTM Type-S/CVI-SiC composites with either (a) a PyC monolayer or (b) a PyC/SiC multilayer interphase. T. Nozawa et al. / Journal of Nuclear Materials 384 (2009) 195–211 199