Abstract

The Fused Filament Fabrication process (FFF) is a well-known and widely used additive manufacturing process to produce mainly prototypes and pilot series using thermoplastic materials. Continuous improvements in printer hardware and the development of suitable materials make its use in end-products conceivable. The additive manufacturing principle allows the production of geometrically complex components, e.g. topology-optimized components, which would be impossible using conventional manufacturing processes. Due to the layer-by-layer printing principle and manifold process parameters, FFF components usually exhibit a complex meso-structure and show strong anisotropy of the mechanical properties. The meso-structure is created by path-based extrusion of the filaments and thus determines the mechanical behavior of the structure. The relationships between meso-structure and mechanical behavior cannot be captured by common design methods. Due to the lack of structural mechanical analysis capabilities, the use of FFF components in end-use applications requires component-specific experimental validation. In this work, an approach for realistic modeling of the meso-structure of FFF components for a finite element analysis (FEA) is developed. The model is based on the actual printing path. Using a Python script, the relevant coordinates can be extracted from the machine code and movements without material extrusion can be removed. Based on the extracted coordinates, a wireframe model of the printing path is generated in a CAD environment. The geometry of the individual filaments as solids is created by sweeping an elliptical filament cross-section along the wireframe model. Subsequently, the generated meso-structure is partitioned and meshed using the FEM software ABAQUS. A study is performed with the aim of investigating the required number of elements, their size and the expected computational effort. The method is validated with tensile experiments. For this purpose, flat tensile specimens with 100% infill and a 0°/90° oriented infill are fabricated and tested. Using the printing path based modeling method, the tensile tests are modeled and simulated in ABAQUS.