Fracture process zone development and length assessment under the mixed-mode I/II load analysed by digital image correlation technique

Abstract

In this paper, the fracture process zone (FPZ) of high-performance concrete (HPC) is investigated under mixed-mode I/II load conditions, and its formation is studied by applying digital image correlation (DIC). The experimental tests are performed on Brazilian disc specimens with central notch (BDCN). The traction-free crack and the FPZ extent ahead of the crack are localised. This is done by modification of the existing methodology for mode I cracks to account for various mixed-mode I/II loading conditions. Analytical and linear elastic fracture mechanics (LEFM) methods for the critical strain are used to find the FPZ extension. Lastly, this paper revisits the analytical formulas used in the prediction of mode I FPZ lengths. These formulas are adjusted to allow for the prediction of the FPZ length in the whole range of mixed-mode I/II load conditions. Experimental results show that the FPZ has a different size for various mixed-mode I/II load conditions.