Research On Low-speed Impact Resistance Of Dart Structure With Negative Poisson’s Ratio

Negative poisson’s ratio structure is a super-mechanical structure that does not rely on the mechanical properties and mechanical properties of materials.Because of its high specific strength,high specific rigidity,high impact resistance and other advantages,it has gradually been used in aerospace,medical equipment,transportation,ships,sports competitions and other fields are widely used.Based on the concave triangular unit cell structure,this paper proposes and designs a dart structure with negative poisson’s ratio effect.The quasi-static compression study is carried out by using a combination of finite element numerical simulation and experimental verification.The influence law of angle parameters and material properties on the negative poisson ratio of dart structure is compared and analyzed.The results show that the dart structure is a metamaterial structure with a negative poisson’s ratio effect.The negative poisson’s ratio effect is caused by the combination of the hypotenuse and base bending deformation and inplane rotation under the load of the concave triangle effect.The negative poisson’s ratio effect of the dart structure is an inherent characteristic and is not affected by the material properties.The poisson’s ratio is positively correlated with the angle parameter,and the minimum value is-2.1.Based on the negative poisson ratio of the dart structure,the low-speed impact study of the dart plate structure at an impact velocity of 4m/s was further carried out,and the impact damage shape,impact velocity and first principal stress were respectively analyzed quantitatively and qualitatively.Based on the speed and the first principal stress as the evaluation index of the structure’s low-speed impact resistance,the relationship between the low-speed impact resistance of the negative poisson’s ratio dart board structure and the angle parameters and material properties is deeply explored.The results show that the dart board structure appears penetrating failure under the impact load,the shape of the impact position is approximately square,the top and bottom materials are partially peeled off,and propagating cracks with random direction are generated.The low-speed impact resistance of the dart board structure has a negative correlation with the angle parameter.Since different materials have differences in elastic behavior and subsequent fracture behavior,their low-velocity impact resistance will be affected by material properties.Compared with the dart board structure whose material is PLA,the structure whose material is photopolymer has better low-speed impact resistance.