This paper aims to analyse the mechanical properties response of polylactic acid (PLA) parts manufactured through fused filament fabrication. The influence of six manufacturing factors (layer height, filament width, fill density, layer orientation, printing velocity, and infill pattern) on the flexural resistance of PLA specimens is studied through an L27 Taguchi experimental array. Different geometries were tested on a four-point bending machine and on a rotating bending machine. From the first experimental phase, an optimal set of parameters deriving in the highest flexural resistance was determined. The results show that layer orientation is the most influential parameter, followed by layer height, filament width, and printing velocity, whereas the fill density and infill pattern show no significant influence. Finally, the fatigue fracture behaviour is evaluated and compared with that of previous studies’ results, in order to present a comprehensive study of the mechanical properties of the material under different kind of solicitations.

No abstract

Rough surfaces have been shown to promote osseointegration, which is one of the keys for a successful dental implantation. Among the diverse treatments proposed to roughen zirconia, hydrofluoric acid (HF) etching appears to be a good candidate, however little is known about this process. In this work, the effect of HF concentration and etching time on the surface topography and chemistry of yttria-stabilized zirconia was assessed.Besides, to understand the etching mechanism, the reaction products present in solution and on the surface were characterized. The results indicate suitable parameters for a fast and uniform roughening of zirconia. The formation of adhered fluoride precipitates on the surface is reported for the first time and highlights the importance of cleaning after etching. Finally, it is shown that monitoring the time allows controlling the surface roughness, smooth-rough transition and fractal dimension, which should make possible the fabrication of implants with an optimal topography.

Currently, surface treatments lead to inducing a superficial layer of several nanometers up to micrometer, which in some cases can be protective. In this experimental work, an oxide layer was generated under different atmospheres (CO2 and steam atmospheres) during the thermal aging treatment of two different maraging grades, 300 and 350. Afterwards, this layer was microstructural and mechanically characterized by advanced characterization techniques at the micro- and submicron length scale to highlight some information related to the generated oxide layer. The results showed that the oxide layer (in both grades) was made up of several compounds like: TiO2, MoO3, hematite (α-Fe2O3), and CoFe2O4, this being the majority compound distributed homogeneously throughout the layer. Furthermore, a nickel-rich austenitic phase at the interphase was mainly made up cobalt ions (Co2+), instead of iron ions (Fe2+), within the spinel lattice.