Mesoscopic homogenization method of mechanical properties of fused filament fabrication structures considering void shapes and filament interfaces

Abstract The Fused Filament Fabrication process (FFF) is an additive manufacturing process for thermoplastic polymers based on material extrusion. It offers a large range of material options and high potential for manufacturing parts with complex geometry. Mechanical properties of parts produced with this method are, however, highly anisotropic and depend on process parameters and resulting inner mesostructures. The relationships between process parameters, mesostructures and mechanical properties are complex. Characteristics of the FFF mesostructures, such as voids and the interfaces between filaments, cannot yet be sufficiently taken into account in macroscopic design methods. In this work, a method for homogenising mechanical properties is developed. This is based on the inner FFF mesostructure: shape and size of the voids are determined using micrographs and the size of the coalescence areas between the filaments is also estimated. Representative volume elements with periodic boundary conditions are then created in a finite element environment and homogenised mechanical properties are derived. These are compared with analytical and experimental values, and the results are discussed. The method presented here provides an approach on how different characteristics of FFF mesostructures can be transferred to macroscopic simulations. Results of the numerical approach are in good agreement with the experimental data.