Notch Sensitivity of Graphite Materials for VHTR

Abstract

Notch effects on strength were investigated for IG-11 and PGX graphite, which were promising materials for core structures of an experimental VHTR in Japan. Notch sensitivity in tensile strength tests decreased as notch radius decreased. Notch sensitivity of IG-11 was higher than that of PGX. Compressive fracture of PGX was in a shear mode, while that of IG-11 was in a mixed mode of shear and transverse splitting. Compressive strength of IG-11 specimens with transverse slits was smaller than that of smooth specimens, which suggested that a shear mode fracture preceded an ultimate transverse splitting. Results of water quenching tests showed that thermal shock fracture resistance of IG-11 could be smaller than that of PGX when a notch with small radius existed. © 1985, Atomic Energy Society of Japan. All rights reserved.