Exploring the impact of thickness, scale and printing sequence on the tensile and fracture properties of PLA specimens fabricated via fused deposition modeling

Geometrical factors play a key role in determining the dimensional accuracy and mechanical properties of additively manufactured components. This research investigates the influence of thickness, scale, and printing sequence on Polylactic Acid (PLA) specimens produced via Fused Deposition Modeling (FDM) with special focus on tensile and fracture properties of the printed parts. The trends of experimental results were then linked to the microstructures and observations on failure mechanisms and the fabrication process conditions. Tensile test results indicate that increasing the build thickness significantly boosts elongation at failure and slightly raises ultimate tensile strength, while downscaling the printed specimens initially causes minor decreases, but further reductions lead to significant drops in mechanical properties due to higher ratio of intrinsic defect to specimen size. Similar to the tensile properties, fracture analyses revealed that larger build thickness and smaller scale of printed parts lead to lower fracture resistance, with an increasing impact by scale reduction, which is attributed to the formation of defects during fabrication and the thermal history of the printed parts. Printing sequence was found to have limited impact on the mechanical performance of the printed parts with effects below 10%. Additionally, a boundary effect model was employed to evaluate fracture behavior of tested specimens, demonstrating its applicability as an engineering tool for fracture prediction of FDM parts with different scales and thicknesses. The findings of this work underscore the importance of considering geometric factors and printing strategies for effective design and failure analysis of additive manufacturing components.