The Motion Characteristics And Mechanical Behavior Of Folding Metamaterial

With the development of science and technology,human are becoming more and more mature to explore and manufacture new materials with special properties.Metamaterials as artificial composite structure or material,has the superior physical properties.The origami and kirigami is an important source of the concept of metamaterials design due to the more flexible adaptability.They have attracted extensive attention in science and engineering fields.In this paper,four different folding mechanical metamaterials are proposed based on the Tachi Miura pattern,the motion characteristics and the quasi-static mechanical behavior were investigated experimentally and theoretically.The effect of original angles and the number of folding layers on the out-of-plane Poisson's ratio was investigated.The results show that with the decreasing of the original angle,the Poisson's ratio of two orthogonal direction varied differently.One of the direction has always been negative,the sign of the other changed many times.Compared with the effect of original folding angle on Poisson's ratio,the influence of the length to height ratio is relatively small.When the number of folded layer is odd,the dimensionless force is better than that of even folded layer.The less of the folded layer number,the larger the dimensionless force.Four different folding structures all exhibited multistable phenomena.With the original folding angle increasing,the relationship between force and the folding rate transformed from the type I structure to the type II.In this paper,the multistable of four folding metamaterials was studied by using deformation vector field.It is found that the dimensionless elastic energy of the folding structure is affected by the original angles.The effect of original folding angle on H-CL2 dimensionless elastic energy is small,but H-CL3,H-CL4 and H-CL5 metamaterials have significant correlation of original folding angle.With the increasing of original folding angle,the minimum dimensionless elastic energy decreases.The multi-stability of four folding metamaterials exhibited same laws.There is a stable state when the original folding angle is smaller.But there are two metastable states if the original folding angle exceeds the critical angle.The quasi-static mechanical behavior of the folding metamaterial was studied by using the Instron 5544 in this paper.The effect of the original folding angle and the number of folding layers on the force-displacement,deformation process and deformation modes was analyzed.The results show that there is a initial peak force of force-displacement curves with the original folding angle increasing.The structure bearing capacity of odd folding layer is better than that of even layer.And the lower the number,the better the bearing capacity.The original folding angles and the number of folding layers have great influence on the deformation modes of the folding metamaterials under quasi-static loading.With increasing of the original folding angle,the deformation mode of the folded specimen transformed gradually from elastic bending coupling with plastic buckling/bending modes to elastic bending coupling with Euler buckling modes.Based on the principle of virtual work,the expression of bearing capacity in rigid folding process of folding metamaterials is derived.Based on the axial compression buckling theory of square tube and the experimental deformation modes,theoretical results of bearing capacity under quasi-static loading is obtained.The strain hardening of the paper is also considered.The theoretical results agree well with the experimental results which could provide a theoretical support for the engineering applications.