A multi-scale homogenization framework for design and strain-gradient modeling of additively manufactured parts fabricated by particulate composites

Classical homogenization approaches applied to heterogeneous materials are suitable for the cases where a scale-separation is eminent. As the length-scale at the effective continuum reaches the length-scale of the microstructure of the material, classical homogenization approaches fail to be accurate. In such cases, higher-gradient theories may be stimulated for multi-scale material modeling of complex structures in terms of geometry and material. In this study, a multi-scale homogenization framework is presented for additively manufactured (3-D printed) composite parts with specific infill design. The overall framework consists of two major steps, namely micro-to-material and material-to-structure homogenization. In both steps, an asymptotic homogenization procedure is applied to determine constitutive parameters. In the micro-to-material homogenization, the constitutive parameters of the composite material are first determined regarding the material composition. Then, in the material-to-structure homogenization, the constitutive parameters are obtained regarding the infill design of the additively manufactured part. The developed two-step homogenization framework is applied for an off-the-shelf composite material commonly used in 3-D printers. Specifically, in this study, composite parts printed with grid infills are investigated numerically considering different infill ratios.