Gear-Driven Metamaterial Design with Continuously Tunable Stiffness

Gears provide an ideal mechanism for the smooth transmission of rotation and heavy compressive loads thanks to reliable gear meshing. This mechanism can effectively achieve a metamaterial structure with continuously tunable stiffness. In this paper, a novel gear-based structure is unveiled with continuously tunable stiffness. This structure consists of gears held by two frames, which can engage and rotate in two perpendicular directions. We explored the mechanical performance of a uniquely designed metamaterial created through 3D-printing, experimentally and numerically. Experimental results demonstrated the reliability and achievement of continuously variable stiffness for the designed gear-based metamaterial structure. The numerical results also confirmed that the mechanical performance and stress distribution change drastically as the gears rotate and that the stiffness can be continuously tuned. The changes in stiffness depending on the gear angle in both directions were also evaluated for the titanium alloy, in addition to metamaterials made of ABS-like, and the results showed that regardless of the material, the practicality of the novel gear-based metamaterial structure with continuously tunable stiffness remains. The stiffness of the structures increased significantly with gear rotation, changing by 33.69% for ABS-like and 73.94% for titanium alloy in the [Formula: see text]-direction as the angle varied from 0[Formula: see text] to 90[Formula: see text] under identical geometric configurations.