Additive Manufacturing of Graded Voronoi Cellular Structures for Increased Design Flexibility

Voronoi cellular structures (VCSs) are multifunctional materials that can be customized to specific design requirements by suitable density gradation. By locally changing the density, their response can be modulated, and therefore, they can be readily adapted to tailored requirements. Despite these merits, their fabrication is a challenge due to the complexities in the topology of their structure. Conventional manufacturing methods are inadequate to produce the designs dictated by specialized requirements. In this study, the technique for the fabrication of 3D VCSs with spatially varying density is developed using additive manufacturing. Open-celled VCSs are additively manufactured using photopolymer jetting technology that allows the creation of complex parts with high accuracy. The data processing required for generating 3D Voronoi models and managing their complex geometrical features is performed using Python scripts. Uniform-density and density-graded VCSs are fabricated by controlling the cell size, which directly influences their local density. Their dynamic response under the impact of a rigid mass is experimentally determined using a drop tower setup. The compression in the specimen is measured using digital image correlation with the help of a high-speed camera. It is observed that the deformation behavior of VCSs can be tailored by local density variation.