Effect of Printing Speed and Core Relative Density on the Mass-Specific Bending Performance of 3D-Printed PLA Re-Entrant Sandwich Structures

This study investigates the bending performance of 3D-printed polylactic acid (PLA) re-entrant honeycomb sandwich structures fabricated using fused deposition modelling (FDM). The effects of printing speed and core relative density on mechanical efficiency were examined using a complete 2×3 factorial set of six parameter combinations, arranged in a mixed-level L6 format for signal-to-noise ratio analysis. Three printing speeds (50, 100, and 150 mm/s) and two relative densities (0.3 and 0.5) were considered, while other printing parameters were kept constant. Three-point bending tests were conducted in accordance with ASTM C393, and the mechanical responses were evaluated in terms of maximum load per mass and bending stiffness per mass to account for weight efficiency. Within the investigated range, increasing printing speed enhanced both maximum load per mass and bending stiffness per mass, whereas core relative density had a greater influence on bending stiffness per mass. Signal-to-noise ratio analysis identified printing speed as the dominant factor for maximum load per mass, while relative density was more influential for bending stiffness per mass. These trends were confirmed by analysis of variance and Pareto chart evaluation. Among the six investigated combinations, a printing speed of 150 mm/s and a relative density of 0.3 produced the highest measured mass-specific load capacity and bending stiffness. This combination represents the best-performing condition within the investigated parameter space and should not be interpreted as a global optimum. Additive-model estimates differed from the corresponding measured means by less than 2%; however, this comparison represents within-sample agreement rather than independent experimental validation. Empirical linear models described 86% of the measured response variation; however, these models are intended only to summarize trends within the tested parameter domain. The findings provide range-specific evidence for selecting printing conditions for comparable integrally printed PLA re-entrant sandwich structures under quasi-static bending.PLA