2008 年 57 巻 7 号 p. 725-731
This paper discusses the fracture criteria for predicting the strength of unidirectional discontinuous glass fiber reinforced composites with side-notches. The point stress criterion (PSC) for notched composites was employed so that the Tsai-Hill criterion for orthotropic materials is satisfied. The fracture criterion proposed on the basis of linear notch mechanics (LNM) proposed by Hyakutake et al. was also discussed in association with the above two criteria. Strength of intact and notched unidirectional composites was experimentally obtained for various kinds of off-axis angle and notch depth. The stress concentration factor in the vicinity of a notch was calculated with the use of finite element analysis. It was found that the notched to intact strength ratio is almost independent of off-axis angle though it slightly depends on notch depth. The characteristic length for the PSC estimated through the above experimental and analytical results increases with increasing off-axis angle and notch depth. The critical maximum stress of the LNM-based criterion was shown to be a function of fiber orientation angle, but almost independent of notch depth. The LNM criterion was proved to be equivalent to the PSC that satisfies the Tsai-Hill criterion.