An investigation on viscoelastic characteristics of 3D-printed FDM components using RVE numerical analysis

Fused deposition modelling (FDM) has emerged as an economical additive manufacturing method having the potential to fabricate functional components. Dynamic behaviour of FDM components is of great interest while designing and printing them for functional applications. This paper presents a methodology to describe the dynamic characteristics of FDM, combining the features of thermoplastic material and build parameters adopted in fabrication. The viscoelastic characteristics of thermoplastic filament induce time–temperature dependence in FDM components. The viscoelastic characteristic of the polymer is determined by dynamical mechanical analysis. Layer height is a significant build parameter that determines void geometry even in 100% infill printing, that influences mechanical properties of these additive manufactured components. Dynamic response of FDM 3D-printed parts is highly dependent on viscoelastic characteristics of polymer filaments and build parameters associated with printing. In the study, micro-scale models representing the features of actual cross section morphology with different layer heights are identified as representative volume element (RVE) models. Harmonic analysis is conducted on the RVE models using polymer material data approximated with generalized Maxwell model to determine the dynamic characteristics of the FDM print. The numerical analysis reveals orthotropic viscoelastic nature with maximum stiffness along the direction of filament deposition (raster) direction followed by transverse and vertical directions. A drastic reduction in the FDM component stiffness was observed at lower straining rates. The characteristics determined on RVE can be homogenized to the entire structure based on its print conditions and can be used for designing functional components.