Time-dependent mechanical response of ice adhesion on metal substrates

Ice adhesion on aerospace-relevant materials is both complex and poorly understood. Measuring and understanding the underlying physics requires reliable testing techniques that can yield multifaceted datasets. The latter includes surface morphology (i.e., roughness and its spatial correlation structure), resolving substrate-induced strain, and direct mechanical testing of adhesion. Our initial creep test data using a stress-controlled rheometer showed an apparent adhesion dependence on both surface roughness and temperature: namely, that the adhesion strength is higher for rougher surfaces and seems to increase with temperature. To shed light on these initial findings, we performed time-dependent stress ramps from -20 to -7^oC to determine the dynamical stress relaxation mechanism. Additionally, we investigated the spatial correlation surface roughness maps for aluminum specimens. Stress-ramp results confirmed a connection between surface roughness and apparent adhesion. Moreover, the creep-test behavior appears to represent an upper bound of the time-dependent adhesive behavior of ice. These results take us a step forward to understanding ice adhesion mechanisms.