A Negative Poisson’s Ratio Lattice Structure With Both Chiral And Re-entrant Property

Negative Poisson’s ratio structure has been widely studied due to its light weight and high strength,sound absorption and heat insulation,energy absorption and other characteristics.These characteristics make it widely used in construction engineering,aerospace,biomedical and other fields.In water conservancy projects,the negative Poisson’s ratio structure is reasonably arranged in the downstream river channel of the spillway dam,and the energy dissipation and impact resistance mechanism of the negative Poisson’s ratio structure are used.In addition,the high-speed water flow fluctuates periodically in the negative Poisson’s ratio structure,and the water body is continuously disturbed to dissipate energy,which avoids the erosion damage to the downstream banks of the dam and the river channel.Inspired by the ancient Chinese window flower structure,this paper carried out a series of studies on the negative Poisson’s ratio structure with both chirality and concave from the perspective of structural design,preparation,characterization and application.The main contents are as follows:(1)The negative Poisson’s ratio lattice structural model with different geometric parameters was designed.The structural model was obtained from the single cell lattice,and the geometric size of the single cell remained unchanged.By changing the length ratio(0.237～7.202)and the deflection angle of the chiral cross(0°～45°),a total of 90 structural models were designed.The typical structural model was prepared by SLA 3D printing.(2)To study the static tensile mechanical properties of chiral and concave structures.Theoretical analysis model,experiment and finite element simulation analysis mutually verify the negative Poisson’s ratio of the structure,in which the theoretical analysis model provides theoretical support for the verification of the accuracy of experimental results.It is found that the negative Poisson’s ratio calculated by experiment and numerical simulation is consistent,and the accuracy of numerical simulation is verified by experiment.This study shows that material parameters have little on the negative Poisson’s ratio.The key of negative Poisson’s ratio structure is to design the structure reasonably and realize negative Poisson’s ratio effect.The combination of chirality and concave deformation is the main factor of negative Poisson’s ratio effect of window structure.(3)The tensile numerical simulation of negative Poisson’s ratio structure was carried out to explore the influence of different length ratios and different deflection angles of chiral crosses on the negative Poisson’s ratio effect.The numerical simulation results show that the influence of geometric parameters on the negative Poisson’s ratio is mainly due to the coordination of chirality and concave structure,and the length ratio has a great influence on the negative Poisson’s ratio,which has a jump property.The deflection angle of the chiral cross has little effect on the negative Poisson’s ratio,which shows a smooth curve.In this paper,the research for the impact in the field of energy dissipation of the protective structure and provide reference for shock resistance,and new materials with negative Poisson’s ratio can be embedded into the traditional water conservancy projects,such as optimizing design of structure is applied to dam flood discharge energy dissipation impingement,not only improve the downstream river channel scour,erosion,bank serious phenomenon,still can form a unique ecological landscape.It is more in line with the concept of green development of water conservancy projects.