STATISTICAL NANOMECHANICS OF ICE AND EFFECT OF EMBEDDED CARBON DIOXIDE
SW Cranford, PROCEEDINGS OF THE ASME 34TH INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARCTIC ENGINEERING, 2015, VOL 8, V008T07A017 (2015).
While the macroscopic mechanical properties of pure ice has been investigated by laboratory tests and its behavior has been characterized by existing fracture mechanics models, the effect of environmental conditions - such as the concentration of embedded carbon dioxide (CO2) - is not fully understood. It is known that the chemical environment can have significant effects on the mechanical properties of ice. Using full atomistic molecular dynamics (MD), we probe the tensile strength of a single ice crystal. We systematically introduce a random concentration of CO2 molecules by replacing H2O molecules on the ice crystal lattice (e.g., substitutional defects). As anticipated, we observe a drop in strength with an increase in CO2 concentration. The decreased ice strength is not merely caused by material defects induced by the CO2 inclusions, but rather by the fact that the strength of hydrogen bonds the chemical bonds between water molecules in an ice crystal is actively disrupted under increasing concentrations of CO2. The inclusions provide both stress concentrations and nucleation points for crack/void formation. We then assume a Poisson distribution to reflect various concentrations of CO2 and apply nanoscale Weibull statistics (NWS) as a brittle material failure model. The results can be used to help predict the strength range of bulk ice.
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