Large deformation of shape-memory polymer-based lattice metamaterials

•Large deformation of ultra-low-density SMP-based lattice meta-structures is studied for the first time.•Distinct deformation mechanisms are observed for different densities.•High shape and force recoverability are achieved for lightweight structures under large deformations.•Tunable shape memory and mechanical properties are achieved through structure design and pre-straining. Through advanced computational analysis, this work demonstrates that metamaterial structures when made by shape-memory polymers (SMPs) can provide unique intelligent mechanical behavior. For the first time, geometrical effects, pertaining to low and ultra-low densities, on the thermomechanical behavior of SMP-based octet-truss lattice meta-structures are studied in this work. A reliable constitutive thermo-visco-hyperelastic model is applied to analyze the shape-memory behavior of several designed octet-truss lattices with ultra-low and low relative densities, ranging from 0.04 to 0.23. Different compressive strain values are tested to determine the effect of pre-straining. It is concluded that changing the relative density as a consequence of altering the diameter of struts in lattice meta-structures is a crucial factor affecting their shape-memory properties, deformation mechanism, and macro-scale mechanical properties compared to the bulk SMPs. The finite element results demonstrate that the relative density and pre-strain level provide two controlling parameters in programming the SMP-based lattice meta-structures and enhancing their stress recoverability. [Display omitted]