UC San Diego

Tunable auxetics is a new field of engineered mechanical matematerials that has gained thrust recently due to improvements in 3-D printing capabilities. Sign tunable auxetic materials thusfar but have been restricted to line symmetry. An existing 4-star auxetic unit cell with square symmetry was modified using additional linkages and concepts from geometric non-linearity to achieve a square symmetry sign-tunable auxetic unit cell actuated by application of a thermal stimulus. A model of a material based on liquid crystal elastomer that can be made either highly thermally active or thermally inactive was incorporated into the design to induce this sign-tunable behavior. Parameter optimization was performed on the geometric parameters to maximize the difference between the minimum and maximum Poisson’s Ratio observed. Extensive parametric Finite Element Method studies were performed using COMSOL Multiphysics to analyze the design’s performance. A three-by-three lattice of the unit cells was compared to the performance of the individual unit cell, and the results showed complete agreement. For further validation, physical testing in an Instron machine with an attached thermal chamber was proposed.