Functionally graded structures existing in nature can achieve adaptive mechanical properties in response to external loadings through optimizing material distribution. In this paper, a family of origami tubes with systematically varied geometrical parameters are designed and their axial crushing behaviors are analyzed numerically to investigate the concept of inducing graded response through geometrical variation. Three rigid origami patterns are chosen to form the graded origami tubes, and three approaches are adopted to vary tube geometries, including changing the dihedral angle, changing the number of units, and the combinations of them. Numerical results indicate that compared with normal tubes with uniform geometry which have reaction forces with periodic peaks of very close magnitudes, graded origami tubes shows reaction force curves that have different peak values at different stages of deformation. As a result, the amount of axial deformation of the tubes depends on the magnitude of external forces. In the optimal case, a reaction force, the peaks of which are approximately aligned along an ascending straight line, is generated by a tube with both varied dihedral angles and number of units. This work demonstrates that systematic geometrical variation in origami tubes has great potential to trigger graded response.

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