Topology Optimization for Additive Manufacturing: Towards efficient and manufacturable structures for multi-physics applications

Abstract

The Additive Manufacturing (AM) paradigm has continued to revolutionize the way products and components are conceptualized, given its procedure of building parts from the ground up, in a layerwise manner, which brings benefits such as part consolidation, performance-driven products, and unparalleled design freedom to build complex geometries, albeit within some constraints. To fully exploit the capabilities of additive manufacturing (AM), Design for AM (DfAM) integrates process constraints early in the design stage, leveraging topology optimization (TopOpt), lattice design, and simulation-based engineering (SbE) as core tools. TopOpt is a gradient-based method that determines optimal material layouts within a domain under governing physics, objectives, and constraints, while multiphysics topology optimization (MTO) - such as thermal-fluid topology optimization (TF-TO) - extends this framework to coupled flow and heat transfer problems. Lattices are architected cellular structures used to tailor effective material properties, enabling lightweighting & heat dissipation, while SbE drives engineering design and decisions through computational simulation. A review of the MTO literature revealed two key opportunities for novelty. First, components subjected to severe thermo-mechanical loading (e.g., gas turbine hardware) often require the simultaneous design of coolant flow channels and lightweight load-bearing regions, which can be addressed using MTO with coupled fluid, thermal, and structural physics; however, challenges remain in handling multiple material phases while ensuring manufacturability. Second, thermal-fluid topology optimization (TF-TO) is increasingly applied to heat-sink design for high-power-density electronics, but remains accessible only through limited commercial tools, while full three-dimensional (3-D) implementations demand substantial computational expertise, resources, and manufacturability integration. Integrating MTO with lattice architecture offers further potential through SbE-based functional grading and AM compatibility, yet existing studies underutilize advanced design methodologies that could yield additional performance gains while lowering the barrier to adoption. In this research, two major TopOpt-based methodologies have been proposed. To address the first opportunity, an FTS-TO framework was created, which integrates load-bearing and fluid-delivery requirements within a unified Fluid-Thermal-Structural topology optimization using a cascaded two-stage formulation. Optimization Stage 1 (OS1) addresses the thermal-fluidic optimization, while Optimization Stage 2 (OS2) performs a design-independent thermo-structural TopOpt initialized from OS1, yielding structures satisfying flow, cooling, and structural constraints. Development focused on OS2, introducing a robust multiobjective TopOpt for stiff, conductive, lightweight designs with manufactured-feature-size uncertainty resilience, later extended from 2-D to 3-D with explicit minimum & maximum size control, and self-supporting constraints. Validating simulations indicate promise in designing structures that include flow, cooling, and structural needs, while incorporating various constraints, including AM. For the second research prospect, hybrid field-driven design techniques were developed, which integrate multi-scale Triply Periodic Minimal Surface (TPMS) lattices and airfoil-type fins with TopOpt-predicted flow fields. The first hybrid technique Lattice-TopOpt (LTO) method, conforms heat-dissipative lattices to optimal flow paths to obtain AM-suitable high-performance heat sinks. 3D printability was validated via pure copper on an EOS M290 LPBF machine, and experimental validation backed up predicted superior thermo-hydraulic performance, including a real-world application to an award-winning electrochemically printed cold plate. The Field-Oriented Fin Placement (FOFP) approach orients low-drag airfoil fins along TopOpt velocity vectors, yielding lightweight heat sinks with significantly enhanced mass-based thermo-hydraulic performance. Overall, this work advances the integration of manufacturability constraints into MTO for additively manufactured heat-sink and cooling applications, with a focus on low user complexity, and is expected to contribute to more efficient thermal management solutions in the energy sector.