MICROMECHANICS AND MACROMECHANICAL PROPERTIES OF AM – FDM PRINTED ABS

One of the main additive manufacturing (AM) technologies is the fused deposition modeling (FDM), in which layers of molten wires of thermoplastic polymers are printed. Printed FDM-ABS possesses an inherent capacity for property modifications as a function of printing parameters. The bridge between structure and mechanical properties is created by micromechanical processes. The measured macromechanical properties are predicted from the morphology and micromechanical properties. The strength of printed FDM-ABS is composed of: the bonding strength between printed layers, the bonding strength between the wires, and the wires’ strength.

For this study, three-points bending specimens were printed in different printing parameters and orientations. Specimens built in the Z-axis direction provide the bonding strength between printed layers, while specimens built in the X-axis or Y-axis direction provide the bonding strength between the wires and the strength of the wires themselves. Specimens printed in a 45° orientation (XY-plane) examine the changes in strength due to the differences in the direction of the extruded wire.

The first specimens’ tray was printed with the lowest quality parameters available. The tensile strength of each specimen was calculated.

There is a difference in the strength between the X-axis and the Z-axis specimens. The bending-machine breaks the bonding between the layers in the Z-axis specimens (brittle fractures), while in the X-axis specimens it stretches the wires (ductile fractures). There is a slight difference in the strength of the 45° oriented specimens, due to differences in the direction of the extruded wire.