Topology Optimisation Using Additive Manufacturing for Lightweight Aerospace Structures: Experimental Investigation of Functionally Graded Lattice Architectures

Additive manufacturing (AM), defined as a layer-by-layer fabrication process driven by digital design data, enables the realisation of geometrically complex structures that are unattainable through conventional subtractive or formative methods. By allowing material placement only where structurally necessary, AM provides unprecedented control over internal architecture, mass distribution, and functional integration. Lightweight structural design is a critical requirement for modern aerospace systems, particularly for unmanned aerial vehicles (UAVs) and small-scale platforms where mass directly governs endurance, payload capacity, and operational efficiency. Topology optimisation combined with additive manufacturing offers a promising route to overcome the inherent limitations of polymer materials by enabling highly efficient internal material architectures.

This study investigates the experimental performance of topology-optimised lattice structures manufactured using fused deposition modelling (FDM) for lightweight aerospace applications. A function representation (F-rep)-based parametric design framework was developed to generate cylindrical lattice architectures with controlled lattice frequency and vertical phase shift. Seventy-eight (78) specimens were fabricated from polylactic acid (PLA) across three infill regimes (30%, 70%, and 100%) and tested under quasi-static axial compression in accordance with ASTM 1621-16. Mechanical performance was evaluated in terms of maximum compressive load and strength-to-mass ratio.

The results show that topology-optimised lattice structures significantly outperform solid reference specimens in mass-specific mechanical performance. The greatest enhancement was observed at 70% infill, where lattice structures achieved improvements in strength-to-mass ratio of up to 68.42% compared to solid specimens. Lattice architectures also exhibited progressive collapse behaviour, indicating improved damage tolerance.

These findings demonstrate that topology-optimised, additively manufactured polymer lattice structures provide a viable and scalable pathway for developing lightweight, structurally efficient aerospace components, particularly for UAV and small-platform applications.