Mechanical Performance of Three-Dimensional Printed Lattice Structures: Assembled Versus Direct Print.

Lattice structures are composed of a collection of struts with different orientations. During slicing, the inclined struts generate multiple disjoint contours along the build direction in additive manufacturing (AM). These contours are substantially smaller in size due to the narrow cross-section of the individual lattice struts, and they can lead to contour plurality in AM processes. Contour plurality reduces the amount of continuous contact region between two successive layers, thus resulting in poor interlayer adhesion, structural integrity, and mechanical properties of the printed lattice structure. A new interlocking and assemble-based lattice structure building approach is investigated by increasing continuity in layers and avoiding support structure to minimize contour plurality. Two lattice configurations in the form of cubic and octet lattice structures are examined. The compressive performance of the designed lattice structures is compared with the traditional single-build direct three-dimensional printed lattice structures. The mechanical performance (e.g., peak stress, specific energy absorption) of the assembled structures is found to be generally better than their direct print counterparts. The empirical constants of Ashby-Gibson power law are found to be larger than their suggested values in both direct print and assembly techniques. However, their values are more compliant for octet assembled structures, which are less susceptible to manufacturing imperfections.