Additive Manufacturability and Parametric Studies on an Extended Three-Dimensional Re-Entrant Auxetic Structure with Angled Struts

Auxetic honeycomb structures have been applied in lightweight sandwich structure and impact energy absorption applications due to their unique deformation performance. Based on the traditional two-dimensional reentrant honeycomb structure, a modified three-dimensional (3D) reentrant lattice structure with negative Poisson's ratio (NPR) is proposed. The studies on fabrication and design parameters are conducted, leading to a new understanding of the effects of these parameters on the printing quality and mechanical properties of such lattice structure with reentrant diagonal struts. Additive manufacturing (AM), specifically laser powder bed fusion, is used to fabricate five groups of 18Ni350 Maraging Steel samples with different geometric and printing parameters. The compression test is conducted to obtain the effects of NPR on the quasi-static stress-strain relationship of the proposed structure. The results show that smaller hatch distance and scan speed for 3D printing process can lead to less porosity level and more complete printing, resulting in larger stiffness and yield strength of the structure. The preferred AM process variables to improve structural quality with thin angled struts (diameter ≤0.5 mm) are presented. Moreover, with the help of the tuned finite element model based on experimental results, parametric analysis is conducted to confirm the effect of design parameters, including reentrant angle, strut cross-section shape, and size, on the compressive properties of the structure.