Competing and global fractures in 2-D compressed crystalline bubble arrays.

In this project we simulate a two dimensional aggregate of slightly adhesive droplets while compressed between two parallel walls, of which only one moves, mimicking the experiment of Ono-dit-Biot[Soft Matter 17, 1194-1201 (2021)].

For highly monodisperse samples, we observe the structure undergo a transition in a fracture event. As the wall moves, the sample, arranged like a hexagonal closed packed crystal, rearranges itself via removing one row of droplets, and gaining one column. We observe two kinds of fracture events: a singular global event, which results in an orderly HCP structure, and multiple competing fractures, which leads to the appearance of defects. In the case of competing fractures, we study their dependence with array size, aspect ratio, and angle of the wall. Competing fractures were not a phenomenon observed in the original experiments: our simulations suggest that this is caused by relatively small size of the experimental arrays (50 or fewer bubbles) and that the compressing walls in the experiment were not perfectly parallel. Changing these either of these conditions increases the frequency of competing fractures in our simulations.