Analytical and numerical modeling of voids in additively manufactured thermoplastic parts

Additively manufactured parts of thermoplastic materials using the Fused Filament Fabrication (FFF) technique
express transversely isotropic characteristics. Those characteristics are related to the FFF technique which leads
to the formation of particular bonds and voids between printed filaments, both of which are investigated in this
study. Tensile testing of printed Nylon samples reveals that the transverse isotropy can be possibly caused solely
by the bond formation. Micro-CT images aid the visualization of long, convex and concave voids extending
parallelly to the printing direction. Finally, novel analytical techniques are presented for the accurate modeling
of the void geometry considering both concave and convex shapes and illustrate a very good agreement with
Finite Element models.