Infill Density Effect on the Flexural Behavior of FFF-Based AM Polylactic Acid Parts

Fused Filament Fabrication (FFF) is an additive manufacturing process with wide use.However, the optimization of certain parameters presents some uncertainties in the FFF process.In the present study, the effect of infill density (ID) on the flexural behavior of Polylactic Acid (PLA) parts printed by the FFF process was investigated.The experimental tests were performed on rectangular parts, according to the ISO 178 standard, with a test speed of 5 mm/min.Parts with several IDs in the 20-100% range were 3D printed, analyzed, and tested.Every sample was subjected to dimensional and mass analyses before the experimental tests.After testing, the failure mechanisms were highlighted depending on the ID.It was found that the ID of the printed parts strongly influences the flexural characteristics (elastic, strength, strain, and energy absorption).However, using the specific properties (specific modulus and specific strength), it was noted that 20%-ID is the optimal density for such AM structures.Slight dependencies on IDs were recorded for dimensional accuracy.It was obtained that at low IDs (<40%), the FFF-printed parts show a quasi-brittle fracture, and with its increase (IDs > 60%), a slight plastic deformation was observed.