Non-uniform pneumatic actuation of elastomeric honeycombs for switchable macroscopic properties
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Honeycomb microstructures with circular voids are well known to undergo pattern transformations under macroscopic strain loading. Depending on the biaxiality of the applied strain, they can deform into three different patterns. We demonstrate that the same three patterns can be triggered also by pneumatic actuation of the circular voids, with patterns being chosen by varying the pressurization scheme, i.e., the ratio of suction pressures applied to different voids within the microstructure. We showcase the evolution of homogenized stiffness and its corresponding anisotropy associated with the pattern forming as a response to pneumatic actuation with a numerical study. We validate the findings experimentally on two finite size samples made of silicone rubber cast in a 3D printed mold, enclosed for the purposes of the experiment between lubricated PMMA sheets. Our results allow up to a 100% variance in macroscopic stiffness between different angles of loading, chosen by a reversible switching process with an actuating mechanism independent of the load itself.