Stress-cognizant 3D printing of free-form concrete structures

Abstract

3D printing enables engineers to design and manufacture geometrically complex structures. As 3D printing technology affords design freedom, it also brings along new challenges. One common property of classical 3D printing is the anisotropy arising from the filament-wise 3D printing process. This anisotropy reduces the load bearing capabilities of the 3D printed part when loaded in its weaker axes, that is the directions orthogonal to the filament. Conversely, by designing the 3D printing path through analyses of its mechanical constraints, the 3D printed part may be strengthened and printed such that it carries the majority of the load in its strongest axis, parallel to the filament (T1), thereby increasing its load-carrying capabilities. We experimentally investigated this idea by designing and printing several concrete samples following two strategies: (i) the classical strategy consisting of parallel rectilinear paths irrespective of the load distribution, and (ii) our proposed strategy consisting of paths that are as much parallel as possible to the principal stress lines. We then subjected the samples to mechanical testing. The test results confirmed that the proposed printing strategy significantly improved mechanical characteristics. Cracking patterns were also observed and discussed.