Page 36 - CBT 2018

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Size effect in fracture and fatigue of quasibrittle materials
The size effect in failure of a quasibrittle material (concrete, rock) is primarily
due to damage localizing into a fracture process zone (FPZ) of finite size. The size effect on strength can be derived from an equivalent linear elastic fracture mechanics (LEFM) model. Further, a size-dependent fatigue kinetics model can be obtained based on the scaling of the apparent fracture energy. In both models, the failure behavior transitions from a plastic type to a LEFM type as the specimen size increases. These two size effect models were validated by strength and fatigue tests on a typical quasibrittle material. Digital image correlation (DIC) and acoustic emission (AE) were used to examine the FPZ at peak stress. The experiments indicated that the size effects on strength and fracture kinetics can be related to each other through the characteristics of the FPZ, supporting a unified energetic scaling model of fracture and fatigue
of quasibrittle materials. [56–58]