In-plane compression behavior of a novel 3D auxetic honeycomb

Abstract

The star-triangular honeycomb (STH) has a unique deformation mode and mechanical properties, especially under low-velocity impact load. This study proposes a novel 3DSTH based on 2DSTH. 3DSTH specimens were manufactured by the 3D printing process, and quasi-static compressive tests were implemented to verify the reliability of the established finite element model. Numerical results show that 3DSTH exhibits a typical negative Poisson’s ratio effect under in-plane compression, and the cells near the platens bend and collapse in the out-of-plane direction. The theoretical analytical formulas of elastic modulus and Poisson's ratio were derived according to the deformation mechanism of the typical cell. The theoretical prediction results match the numerical simulation results accurately. In addition, the parameter analysis shows that the elastic modulus decreases firstly and then increases with the increase in the inclined angle, showing a quadratic parabolic relationship. However, the Poisson’s ratio only increases monotonically with the increase in the inclined angle. Subsequently, the angle and thickness gradients of 3DSTH with different distribution patterns were constructed. The influences of gradient distribution on deformation mode and energy-absorbing characteristics of 3DSTH were studied by performing a comparative analysis. The bidirectional gradient distribution is more conducive to improving the deformation stability and energy absorption characteristics of 3DSTH than the unidirectional gradient distribution. Moreover, 3DSTH exhibits more excellent deformation mode and energy absorption characteristics, approximately 25.45% higher than that of 2DSTH with the same geometric parameters. This study is mainly expected to create some new ideas for the design of the auxetic structure.