<p>Improving the mechanical properties of a bio-sourced polymers by introducing cellulose-based fibers not only opens the way for the future development of sustainable materials, but also for new ways of low-cost additive manufacturing. In this paper, Polylactic acid reinforced with short flax fibers, was used for the fabrication of the architected materials. The process of additive manufacturing is employed as a method of execution. Antitrichiral honeycombs and structural sandwiches have been fabricated through 3D printing. The samples were constructed by varying the relative densities of the auxetic core, specifically using three different densities. Quasi-static tests were conducted on the architectural cores as well as the sandwich structures. The main aim of these evaluations was to determine the tensile properties of the cores and elastic properties of sandwiches under 3-point bending tests. In addition, acoustic emission technology (AE) is used to monitor and quantify the failure mechanisms of the antitrichiral cores and sandwich materials. Experimental results show that the auxetic behavior of honeycomb materials varies with the relative density of the base cell. Poisson’s ratio varies from − 0.25 to 0.5, influenced by the length of the unit cell ligament. Good bending properties were observed for high relative density sandwiches.</p> Graphical Abstract <p></p>