Mechanical properties of 3D printed parts: Effect of ultraviolet PLA filaments ageing and water absorption

In additive manufacturing, fused deposition modelling (FDM) is one of the most often-used technologies. Polylactic Acid (PLA) is the most frequently applied polymer for prototyping or for real uses. This study mainly focuses on the mechanical properties of PLA parts printed with filament exposed to UV light to mimic the effect of recycled filament. Three radiation periods were studied, respectively, 24 h, 48 h and 72 h. Tensile tests were carried out to characterize the influence of building orientation (On flat/on-edge) and raster angles (0°, 45°, 90°, 0°/90°, −45°/+45°). Failure modes were also discussed. Printed specimens were subjected to water absorption to assess the mechanical properties in real application. Generally with the same raster angle, the interlayer structure of specimens manufactured in on-edge orientation has greater adhesion than the specimens in flat orientation. The results show that mechanical properties are lower in case of flat building orientation and the raster angle has the same trend in both orientations. Elsewhere, edge orientation exhibited lower water absorption thanks to the inwall that protected the printed part. UV radiation enhances the interface between printed layers for the lower period. The mechanical properties were affected by the degradation of the bulk material in the direction of 90°.