Early prediction of macrocrack location in concrete, rocks and other granular composite materials
Nature Research, 2020, 10: 20268
AntoinetteTordesillas*, Sanath Kahagalage, Charl Ras, Michał Nitka, JacekTejchman
Heterogeneous quasibrittle composites like concrete, ceramics and rocks comprise grains held together by bonds. The question on whether or not the path of the crack that leads to failure can be predicted from known microstructural features, viz. bond connectivity, size, fracture surface energy and strength, remains open. Many fracture criteria exist. The most widely used are based on a postulated stress and/or energy extremal. Since force and energy share common transmission paths, their fow bottleneck may be the precursory failure mechanism to reconcile these optimality criteria in one unifed framework. We explore this in the framework of network fow theory, using microstructural data from 3D discrete element models of concrete under uniaxial tension. We fnd the force and energy bottlenecks emerge in the same path and provide an early and accurate prediction of the ultimate macrocrack path C. Relative to all feasible crack paths, the Grifth’s fracture surface energy and the Francfort–Marigo energy functional are minimum in C; likewise for the critical strain energy density if bonds are uniformly sized. Redundancies in transmission paths govern prefailure dynamics, and predispose C to cascading failure during which the concomitant energy release rate and normal (Rankine) stress become maximum along C.