Study On Design And Mechanical Properties Optimization Of Negative Poisson’s Ratio Hierarchical Composite Structure

The negative Poisson’s ratio material has a broad application prospect because of its excellent mechanical properties,but it is restricted by the lack of bearing capacity.Octet-truss structure is a truss structure dominated by tension,which has high specific strength and stiffness.The concept of hierarchical structure improves the flexibility of structural design.It can combine structures with different mechanical properties at different structural levels to produce mechanical metamaterial structures with higher performance.At present,the research on the three-dimensional hierarchical structure of negative Poisson’s ratio materials is still lacking.In this paper,the concept of hierarchical structure is used to combine octet-truss structure with negative Poisson’s ratio structure,and its mechanical properties and application are deeply studied,which provides ideas and guidance for the design of new hierarchical structure.In this paper,the finite element software ABAQUS is used to simulate the structure,and some experiments and theoretical analysis are used to verify the results.The specific research contents are as follows:(1)A hierarchical octet-truss structure is proposed by replacing the solid strut of octahedral truss structure with hollow rod with concave hole.Taking the width of the concave rib as a variable,the equivalent Poisson’s ratio,equivalent stiffness and energy absorption efficiency of the concave rib are analyzed by experiment and finite element simulation.Then the influence of relative density and grading on the mechanical properties of the concave rib is discussed.(2)Based on a two-dimensional concave negative Poisson’s ratio structure with high stiffness,several different concave negative Poisson’s ratio structures are topologically designed,and the tubular porous structure is constructed by coordinate transformation.The mechanical properties of four kinds of tubular porous structures were predicted by finite element simulation.Then,four different tubular porous structures are applied to four different lattice structures,and the mechanical properties of the first-order hierarchical lattice structure are studied by finite element simulation.The effects of different cell topologies on the mechanical properties of different lattice structures are discussed.(3)In contrast to the idea of establishing hierarchical octahedral structure,a new hierarchical concave structure is designed by replacing the rib of concave structure with octahedral lattice structure.Then the failure mode diagram of the structure is obtained by theoretical calculation.The influence of the number of octahedral elements on each rib and the ratio of length to diameter of octahedral members on the mechanical properties of the structure is discussed.(4)In this paper,octahedral structure is applied to sandwich panel.Firstly,a two side tube sandwich structure is designed and its quasi-static mechanical properties are studied.Then the composite sandwich panel with hierarchical octahedral truss structure is designed,and its three-point bending mechanical properties are studied,and the mechanical properties of composite sandwich panel with positive Poisson’s ratio hole and negative Poisson’s ratio hole are compared.(5)The mechanical properties of composite equivalent sandwich plates with isotropic negative Poisson’s ratio sandwich subjected to blast loading were studied.The influence of randomness and triaxial compression ratio of random structure on antiknock performance is discussed.