Deicing Strains and Stresses of Iced Substrates

The performance of low ice adhesion or icephobic coatings might be improved by adding a mechanical energy component via an underlying low powered electro-deformable substrate. The strain could be generated with many types of smart actuators consisting of piezoelectric devices, shape memory alloys (SMAs), conductive polymers, or ionic membrane polymer composites (IMPCs). An important step in designing a new electromechanical deicing system would consist of measuring the level of strain needed within an iced substrate to break and shed ice at the interface. In this paper are presented the results of an experimental investigation, in which new set-ups were built and used to simulate the behaviour of an active iced electromechanical substrate generating three types of strains: tensile, torsion, and bending. A total of 174 icing/deicing tests were conducted with aluminum and polyamide test specimens covered with hard rime ice deposits 2, 5 and 10 mm thick and stressed at -10 degrees C at various strain rates in the brittle ice regime. Real time strains and forces were precisely monitored using strain gages and load cells. The stress was calculated from the deicing strain edeicing and force measured at time of deicing corresponding to an interfacial failure between ice and substrate and/or cohesive failure of ice. Under test conditions used, strains were found to be very similar in torsion and in tension but about ten times lower in bending. Moreover, stresses and strains at deicing were found to increase with increasing substrate roughness and decrease with increasing ice thickness. (C) Koninklijke Brill NV, Leiden, 2012