Polymer additive manufacturing (AM), or 3D printing, has been transiting from demonstrative prototypes to functional products that are impacting a wide variety of sectors, from biomedical, electronic, and automotive to aerospace industries. However, the reduced fracture performance often observed in 3D printed parts limits their applications to end-use load-bearing components. This study aims to develop a multiscale modeling framework to predict anisotropic fracture properties of 3D printed polymers for enhanced performance. The approaches involve: 1) Homogenization of microscopic models to predict anisotropic properties at macro scale, 2) Anisotropic phase field fracture models and extended finite element method (XFEM) to predict AM process-dependent crack initiation and propagation patterns. Micro-CT images are used to quantify microstructures and porosities of 3D printed polymers to set up representative volume element (RVE) models. The predictions are validated by experimental test results of samples printed at various build orientations and raster angles. Numerical parametric studies further show that the inter-filament bonding strength could be tuned to create alternate crack paths for maximum fracture energy. Finally, toughening mechanisms using 3D printed topological patterns on the surface to deflect crack paths are explored. This study sheds light on predicting fracture of 3D printed materials for enhanced performance.

Multiscale Modeling of Fracture in 3D Printed Polymers for Enhanced Performance

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