Higher stiffness hierarchical embedded strengthening honeycomb metastructure with small negative Poisson’s ratio reduction

The negative Poisson’s ratio behavior of metastructures is usually achieved through the uneven structural stiffness distribution caused by the artificial pores in the material. However, the large porosity causes the poor stiffness and lowers the load capacity. The previous stiffness enhancement method inevitably caused a great reduction of negative Poisson’s ratio. In this paper, a hierarchical embedded strengthening method is proposed to enhance the stiffness greatly in Honeycomb Metastructure while it still maintain the large negative Poisson’s ratio. Both simulations and experiments demonstrate that our proposed design method can increase the normalized elastic modulus by 3.62 times despite the small negative Poisson’s ratio reduction of 13.79%. This result is far superior to the negative Poisson’s ratio reduction of 66.38% of the traditional strengthening method while the normalized elastic modulus increases by only 2 times. The hierarchical embedded strengthening method provides a new path for applications requiring larger negative Poisson’s ratio and higher elastic modulus simultaneously.