The Graded Origami Structures

There are many excellent graded structures existing in nature to optimize the mechanical properties in various load situations by adjusting the distribution of materials.In this thesis,rigid origami and graded structure concept are combined together to form the graded origami metamaterials.The first part of the thesis focuses on the methods to form graded rigid origami patterns.Three independent methods are proposed,including changing the length of crease lines,changing the sector angle,and changing the number of units.One of the most famous rigid origami patterns,Miura-ori,is chosen to generate the graded origami structures,and the geometric parameters and properties are studied briefly.In the second part,derivative Miura patterns,Arc-Miura and Arc pattern are selected to achieve the graded origami tubes.The geometric parameters and corresponding relationships are explored.The third part is devoted to the engineering applications of these structures.Numerical simulations based on the finite element method are employed to assess the mechanical properties,in which quasi-static three-point bending response of sandwich beams with graded Miura-ori core and quasi-static impact response of graded origami tubes are explored.The investigation reveals that sandwich beam with graded Miura-ori core have preferable energy absorption capability in three-point bending compared with the normal Miura-ori core.Manufacturing of origami patterns forms the final part of the thesis.Prototypes of rigid and non-rigid origami pattern are generated using 3D printer.Their crease lines and panels are printed by different materials,one is the soft material and the other is hard material.This manufacturing method is applicable to various origami patterns,which shows timesaving.