Nonlinear stiffness analysis and programming of a composite origami metamaterial with embedded joint-type metastructures

Origami metamaterials have tremendous application potential in the fields of advanced deployable mechanisms, intelligent robots, and energy absorption devices. In this paper, we embed the flexible joints with metamaterial properties into the origami metamaterial structure, making the origami mechanism have simultaneous geometric nonlinearity and joint stiffness nonlinearity, and investigate the nonlinear stiffness characteristics of this composite metamaterial in detail. To enhance the bearing capacity of the overall structure, the tension spring is mounted to simulate the elastic effect of the crease, and the mechanical metamaterial property of this flexible joint is also revealed theoretically. Based on the kinematics of Miura-ori pattern, the static nonlinear mechanical properties of the composite metastructure are obtained. Besides, the detailed parameter analysis gives an effective validation of the strong design flexibility of the proposed origami mechanism, and the stiffness property programming is realized by tuning structural parameters. Finally, an experimental system is established to test the static mechanical properties of the flexible joint and the origami mechanism, and the high agreement between experimental curves and theoretical results confirms the effectiveness and practicality of the composite metamaterial. This work is helpful for the design of origami metamaterials exploiting their stiffness nonlinearity.