Effect of filler density on the mechanical properties of poly-lactic acid (PLA) samples produced in 3 dimensional (3D) printer

In this study, mechanical, thermal and cost analyses of PLA (Polylactic Acid) samples produced by 3D printer were performed and the effects of polyurethane foam and epoxy resin fillers on these properties were investigated. PLA samples with 10% and 20% filling ratios prepared in accordance with ASTM D638 and D5023 standards, were supported with fillers and subjected to mechanical tests such as tensile and bending tests. Additionally, Scanning Electron Microscopy and Thermal Gravimetric Analysis methods were used to examine the distribution and thermal behavior of the filling materials. According to the tensile test results, polyurethane foam filling increased the rigidity of PLA by 16-22%, but only provided a limited improvement of 10-15% in maximum stress and elongation values. In contrast, epoxy resin filler increased the mechanical strength of PLA, providing an increase of up to 20% in maximum tensile values and up to 15% in elongation values. In the bending test results, the control group (PLA without filler material) had the highest elastic modulus (3177 N/mm²) and maximum tensile values (91.59 N/mm²), while a 10-30% decrease in these values was observed in the PLA samples supported with filler materials. However, epoxy resin-filled PLA exhibited 15% better mechanical performance compared to polyurethane-filled PLA. Thermal analysis showed that the polyurethane filler slightly decreased the thermal stability of PLA by 5-7%, while the epoxy resin increased the thermal stability by 8-10%. SEM images revealed that the polyurethane filler was unevenly distributed in the matrix, leading to clusters, while the epoxy resin formed a more homogeneous distribution and strong interfacial bond with PLA. Cost analysis results showed that polyurethane-filled PLA is suitable for low-cost applications, while epoxy resin-filled PLA is advantageous for applications requiring high performance, although its cost is 19% higher. In conclusion, this study demonstrated the potential of fillers to improve the mechanical and thermal properties of PLA, and emphasized the need to optimize the filler type and filling ratio. This study shows that PLA can be customized and adapted to different industrial fields.