Deformation characteristics and mechanical properties of a non-rigid square-twist origami structure with rotational symmetry

Non-rigid origami patterns could provide more versatile performance than their rigid counterparts in the design of mechanical metamaterials owing to the simultaneous deformation of facets and creases, but their complex deformation modes make quantitative characterization and programmability of mechanical properties a challenging task. Here, we investigated the tensile behavior of a non-rigid square-twist origami structure with rotational symmetry by combining biaxial tension experiments and finite element modeling. A three-stage deformation process, including tightening, unlocking, and flattening, of the structure was unveiled through a detailed analysis of facet distortion and crease rotation, and the relationship between structure deformation and several key features in the energy, force, and stiffness curve was obtained. Based on the analysis, an empirical model was built to correlate the geometric and material parameters of the structure and its deformation energy, initial peak force, and maximum stiffness, which were further validated through experiments. Using the model, the mechanical properties of the structure can be accurately predicted and programmed based on specific engineering requirements, thereby serving the development of new programmable mechanical metamaterials based on the family of square-twist origami.