Molecular dynamics modeling of cracks in dry clay sheets at the nanoscale

Z Zhang and XY Song, COMPUTERS AND GEOTECHNICS, 152, 105037 (2022).

DOI: 10.1016/j.compgeo.2022.105037

Clay is a nanomaterial by nature. The cracking in clay at the nanoscale can provide significant insight into the cracking mechanism in clay at the continuum scale. This article is devoted to understanding the atomic-scale mechanism of the formation of cracks in a dry clay sheet through molecular dynamics with a general force field for clay. We simulate the formations of mode I and mode II cracks in intact dry clay sheets under tension and shear loading conditions, respectively. The numerical results show that the mode I and II cracking in a clay sheet is brittle and strain-rate dependent. The notion of critical bond stretch is adopted to model the breakage of bonds between atoms in clay. The critical bond length for crack formation is determined by the radial distribution function and the force curve between a pair of atoms. We investigate the crack initiation under mode I and mode II loading conditions from the bond breakage analysis. We interpret the cracking mechanism in terms of the type and number of broken bonds in mode I and mode II cracking. We present the stress intensity factor and cracking energy release rate under both cracking modes. The numerical results of the stress intensity factor and cracking energy release rate are quantitatively comparable to the experimental and numerical data in the literature.

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