Numerical Investigation of Metamaterial Unit Cells with Tunable Mechanical Behavior Under Quasi-Static Uniaxial and Torsional Loads

Mechanical metamaterials and programmable materials exhibit adjustable mechanical properties and are therefore of great interest to many application areas in academia and industry. Due to their complex, filigree geometry, they are usually additively manufactured, which causes a large variance in the manufacturing-related mechanical properties. In this paper, a load-torsion-coupling behavior together with a tunable stiffness property was numerically investigated based on different modifications of a bcc unit cell. Further, the mechanical response of manufacturing induced geometrical distortion was examined. The considered load conditions were uniaxial and torsional loads. The implementation of tunable stiffness in compression increased the resulting maximum stress up to five times for all models. A load-torsion-coupling in uniaxial and torsional direction was maximized when all upper struts of the unit cell were bent while all struts of the bottom part were straight struts. The combination of tunable stiffness in compression with load torsion coupling influenced the resulting torque beyond the contact point. Finally, manufacturing induced geometrical distortions are best detected by the evaluation of resulting stresses and moments in all spatial direction.
The obtained results show the potential of the combination of different response characteristics and the need of new experimental validation methods.