Flexural strength and weight optimization of infill sandwich and honeycomb sandwich structures made of PLA/lW-PLA using the FDM method

In this experimental study, the weight and density variations of infill and honeycomb sandwich structures produced by the Fused Deposition Modeling (FDM) method were systematically investigated. Pure PLA was used in the face sheets, while a novel lightweight material, LW-PLA, was employed in the core structure to achieve significant weight reduction. The foaming behavior of LW-PLA printed at 200 °C, 220 °C, 240 °C, and 260 °C was characterized through density measurements based on Archimedes’ principle and thickness measurements of single-layer shell specimens. Based on the experimentally determined foaming ratios at different printing temperatures, the extrusion parameters of the 3D printer were redefined and optimized. The flexural behavior of the sandwich structures was evaluated by three-point bending tests, and the mechanical performance was directly compared with structural weight. Core structures printed at 260 °C and 240 °C achieved weight reductions of 56% and 52%, respectively. In terms of bending load and specific performance, the best results were obtained at these temperatures. The combined evaluation of strength and lightness indicates a net performance improvement with the use of LW-PLA. The results demonstrate that controlled foaming of LW-PLA provides an effective approach for producing lightweight and mechanically efficient sandwich structures by FDM.