Fiber Reinforcement of 3D Printed Concrete by Material Extrusion Toolpaths Aligned to Principal Stress Trajectories

Abstract

Additive manufacturing of cementitious materials is a rapidly growing branch of manufacturing both in research and industry, particularly the variant of material deposition by extrusion. This process results in a strong anisotropy in mechanical properties, owing largely to the interfaces between adjacent filaments. This anisotropy is even more pronounced when fiber reinforced mortars or continuous entrained reinforcement components such as cables are used. To exploit orientation-dependent performance, the print path can be designed to align with the principal (tensile) stress trajectories. However, obtaining an appropriate print path based on this concept poses several challenges, related to the filling of intermediate spaces between two trajectories. In this paper, an approach for planning such a robot toolpath is presented, elaborated, and illustrated by means of a case study on a well-known reference case. The main features of the tool planning method are the relaxation of the offset width, the avoidance of toolpaths with acute angles by intersecting offset curves, and a continuous toolpath.