Structural Layout Optimization of AAM Aircraft at Concept Level - A Comparison of Approaches

This paper compares three concept-level topology-optimization strategies, an Altair’s voxel-based C1 workflow, a shell-only formulation, and a hybrid local voxel/shell approach, applied to a generic eVTOL fuselage to evaluate their ability to reveal primary load paths and their practical computational trade-offs. Using a common geometry, consistent load cases and an OptiStruct-driven topology framework, this work evaluates how 3D voxels, 2D shells, and localized solid volumes influence discovered load paths, convergence behavior, and practical design insight. The voxel (C1) approach explores the full interior volume and frequently reveals internal truss‑like members and non-intuitive architectures, offering rich conceptual information but at a higher computational cost. The shell‑only method produces clear surface stiffening patterns with fast turnaround and low resource needs, but cannot represent discrete internal frames. The hybrid method targeted voxel regions embedded within a thin shell envelope often reconciles global shell trends with locally resolved internal geometry, though effectiveness varies by region. Rather than prescribing a single best technique, the study highlights complementary strengths: shell models for rapid exploration, voxel models for deep discovery, and hybrid refinements where interior layout is critical. These findings provide practical guidance for resource‑aware, multi‑step topology workflows in Advanced Air Mobility concept design and identify directions for future hybrid method development.