Fracture of Ice at Interfaces from Molecular Dynamics Simulations

Ashfar, A., Zhong, J., Thompson, D., & Meng, D. (2018). Fracture of Ice at Interfaces from Molecular Dynamics Simulations. 2018 Atmospheric and Space Environments Conference, AIAA AVIATION Forum, (AIAA 2018-3017). Atlanta, GA: AIAA. DOI:10.2514/6.2018-3017.

We use molecular dynamics simulations to investigate adhesion strength of ice slabs on structured graphite substrates. Adhesion strength is reported as the maximum interacting forces between water and carbon molecules resulted from displacing ice and substrates apart from each other. Molecular level information from simulations indicates that there exists a region in the vicinity of the water-graphite interface where ice crystal structure is disrupted, showing reduced order parameter but high number density. The stress distribution analysis suggests that stresses are concentrated in this disordered interfacial region, and therefore its structure has direct effects on measured adhesion strength. Topology of graphite substrates (“smooth” versus “grooved”) is seen to be a factor in determining ice structure in the interfacial region. On substrates with “grooves” of different widths (greater than three times diameter of water molecule), interfacial structures are found to be similar to each other. Similarity in structure also implies that measured adhesion strength depends linearly on the ice-substrate contact area, which is further confirmed by direct force measurements in our simulations. On “smooth” substrate, however, interfacial structure is observed to be different in exhibiting reduced structural ordering compared to that on “grooved” substrates. Consequentially, measured adhesion strength on “smooth” substrate deviates from the linear contact area dependence by showing a much weaker strength than expected.