Integration of additive manufacturing process-induced material characteristics into topology optimization

Abstract

Motivated by the mismatch between the mechanical performance calculated numerically in topologically optimized designs and that observed in the associated parts fabricated by additive manufacturing (AM) processes, we integrate material characteristics produced via AM processes into topology optimization at low computational cost, by introducing a density-based topology optimization formulation that designs coated structures composed of anisotropic materials. Literature reveals that microstructures and the resulting elastic properties of AM-fabricated parts are affected by local characteristics such as scan pattern and local part shape, which results in material anisotropy and heterogeneity. To account for properties of as-built additively manufactured parts, our formulation for design of coated structures produces anisotropic structures and accounts for heterogeneous material properties in local regions such as near the surface. The formulation takes the form of a multi-material volume-constrained compliance minimization problem and adopts a material interpolation scheme that accommodates material anisotropy and extracts the solid-void interface to enforce the coating. We present a range of examples in 2D and 3D to demonstrate the key ideas, in which a more general volume constraint setting is defined that allows the coated structure design method to accommodate multiple local or partial volume constraints, so as to facilitate flexibility of the volume constraint definition. Lastly, we prove by experimental validation that the integration of AM specific material characteristics in topology optimization generates more optimal designs for fabrication by AM.