T Nozawa et aL /Joumal of Nuclear Materials 384(2009)195-211 200+ UD Hi-Nicalon Type-S v=03,Voe=015 D CTE[10-6/c] F 1打 H 200 Pyc Interlayer Thickness [nm] Fig. 10. Effect of the fiber surface roughness on residual radial stress at the F/M interface In calculation, the fixed CTEs were applied: 4.4x 10-/c for the matrix and UD Hi-Nicalon Type-S V=03Voe=0.15 200+ Roughness=0nm A 兰三三 CTE[10-/C E Roughness=20 nm 400 H Pyc Interlayer Thickness [nm Fig. 11. Thermal residual stresses at the F/M interface vs. Pyc interlayer thickness with varied CTEs of the fiber and interphase. In calculation, the CTE of 4.4 x 10/C was fixed for the matri PyC induces residual tensile stresses at the interface From the lim- believed that the condition under which irradiation-induced swell ted swelling data in 35, no clear turn-around would, however, be ng would not become a critical concern. However, this may not b nticipated. In contrast, the axial stresses in the fiber and matrix an appropriate assumption, especially in the low neutron dose become much more tensile and compressive by neutron irradia- range, in which swelling-induced stress would become analytically tion, respectively. Specifically, the axial stress in the matrix analyt significant( Fig. 12). However, there might not be a critical concern ically saturates with increasing neutron dose( Fig. 12). considering stress relaxation by irradiation creep. For the evalua- tion on the interfacial shear properties, this residual stress issue, 4.2. Effect of neutron irradiation on interfacial shear properties therefore, needs to be clarified first of all. Though the importance of irradiation-induced stresses is recognized, their contribution In preliminary work by the authors [13]. the effect of swelling cannot be quantified completely at this moment since understand on the F/M interfacial strength was disregarded because it has been ing of the swelling behavior and irradiation creep is insufficient.PyC induces residual tensile stresses at the interface. From the lim￾ited swelling data in [35], no clear turn-around would, however, be anticipated. In contrast, the axial stresses in the fiber and matrix become much more tensile and compressive by neutron irradia￾tion, respectively. Specifically, the axial stress in the matrix analyt￾ically saturates with increasing neutron dose (Fig. 12). 4.2. Effect of neutron irradiation on interfacial shear properties In preliminary work by the authors [13], the effect of swelling on the F/M interfacial strength was disregarded because it has been believed that the condition under which irradiation-induced swell￾ing would not become a critical concern. However, this may not be an appropriate assumption, especially in the low neutron dose range, in which swelling-induced stress would become analytically significant (Fig. 12). However, there might not be a critical concern considering stress relaxation by irradiation creep. For the evalua￾tion on the interfacial shear properties, this residual stress issue, therefore, needs to be clarified first of all. Though the importance of irradiation-induced stresses is recognized, their contribution cannot be quantified completely at this moment since understand￾ing of the swelling behavior and irradiation creep is insufficient. Fig. 10. Effect of the fiber surface roughness on residual radial stress at the F/M interface. In calculation, the fixed CTEs were applied: 4.4 106 /C for the matrix and 5.1 106 /C for the fiber. Fig. 11. Thermal residual stresses at the F/M interface vs. PyC interlayer thickness with varied CTEs of the fiber and interphase. In calculation, the CTE of 4.4 106 /C was fixed for the matrix. 206 T. Nozawa et al. / Journal of Nuclear Materials 384 (2009) 195–211