Mechanical properties, structure and fracture behaviour of additive manufactured fff-abs specimens

The Fused Filament Fabrication (FFF) method is one of the most important additive manufacturing (AM) technologies. This technology is used today with various kinds of thermoplastic materials, including ABS. The present study deals with the flexural strength and axial deflection of ABS specimens versus relative density, to observe the influence of build-orientations, build model and microscopic level defects of these properties. In this study, the mechanical and structural characterization of AM-FFF ABS material was studied by CAD modelling of different orientations, three point bending mechanical testing, visual testing, and multifocal light microscopy observation, including fractography analysis. To that end, three different standard building orientations (Flat, On Edge and Upright) were printed, and each was built in two different angle orientations (-45^o/+45^o and 0°/90^o). Based on the three point bending testing results, it was found that the specimen with the highest flexural strength was not necessarily the one with the highest deflection. It was also observed that On Edge 0/+90^o orientations showed a relatively larger flexural strength difference in comparison to other building orientations (Flat and Upright). When the mechanical properties achieved from a bending test next to the building platform were compared to the properties far from the building platform, only a slight difference was found, which means that the flexural strength difference results from the building strategy and it is not related to the specific bending surface. Based on fractography observation, there is a major difference in the mechanical properties and fracture surface appearance, when the samples are bent between the layers (Upright orientation) or when the samples are bent through the layers (Flat and On Edge orientation).