Investigation of the effect of individual and combined weathering factors on mechanical properties and degradation of PLA FFF 3D prints

This study investigates the effects of isolated and combined weathering factors (UVA/UVB radiation, high and low temperatures and humidity) on the mechanical properties and microstructure of PLA 3D prints fabricated using Fused Filament Fabrication (FFF) technology. Specimens were subjected to accelerated aging simulating a one-year exposure in a temperate climate and subsequently analyzed via tensile testing and scanning electron microscopy (SEM). The results demonstrate that the impact of these weathering factors exhibits a strong synergistic effect. While individual exposure to low temperatures, moisture, and UV radiation reduced the ultimate tensile strength by 9% to 12%, exposure to elevated temperature and combined weathering led to a paradoxical increase in strength by 27% and an increase in material density. SEM analysis confirmed that this phenomenon was driven by accompanying annealing, which promoted interlayer sintering. However, under the combined weathering, this strengthening was accompanied by surface degradation and a 22% reduction in elongation at break and a change in fracture failure mechanism from brittle trans-raster failure to inter-bead failure with tendencies to delamination.