Inverse design of compression-torsion mechanical metamaterials with suppressed Poisson effect under large deformation

The intrinsic coupling of torsion (shear) properties with the Poisson effect is typical of the chiral materials subjected to compressive loads. Pure torsion functionalities with suppressed Poisson effect are of great interest for innovative actuators capable of switching displacement modes in confined or specialized assembly spaces. However, both the torsion property and Poisson effect may be dependent on the strain, which makes it challenging to design the constant torsion functionality with zero Poisson effect under large deformation. This study develops an inverse design method of a compression-torsion mechanical metamaterial with a suppressed Poisson effect. In the method, a nonlinear representative volume element model is built to characterize the coupling deformation behavior under large compression strain. Then, a topology optimization model is formulated to provide a high-dimensional design space, and it maintains high computational efficiency via the representative volume element model. Freeform microstructure topologies with tailored torsion functions and near-zero Poisson’s ratios are generated by this topology optimization formulation. The performance of the designed microstructures is validated at both the microscale and macroscale. Furthermore, experiments show the torsion angle of the metamaterial cylindrical shell is tunable via local confinement, overcoming the difficulty of reconstructing the metamaterial to change the torsion functionality.