A numerical study of additively manufactured lattice structures for bird strike resistance in UAV leading edges

Bird strikes remain a major threat to lightweight composite aircraft structures, particularly leading-edge (L.E) components that experience severe impact loading. This study investigates the bird-strike performance of a composite UAV L.E reinforced with additively manufactured lattice structures using three topologies (Body-Centred (BC), Body-Centred Cubic (BC-cubic), and Face-Centred Cubic (FC-cubic) combined with uniform (1.5 and 2.0 mm) and functionally graded (1-2 mm) strut configurations. A validated Abaqus/Explicit finite element model employing a Smoothed Particle Hydrodynamics (SPH) bird model was used to evaluate the structural response. The influence of lattice topology and functional grading on stress transfer, energy absorption, plastic deformation, structural displacement, and mass efficiency was systematically assessed. The results show that lattice topology governs the impact load-transfer mechanism, whereas functional grading improves structural efficiency through optimized material distribution. The BC topology promoted extensive lattice deformation and high specific energy absorption but resulted in larger structural deformation and increased loading of the composite skin. In contrast, the FC-cubic topology exhibited higher stiffness but transferred a greater portion of the impact load to the composite, causing localized damage. The BC-cubic topology achieved the most balanced response by concentrating plastic deformation within the lattice while preserving the composite skin. Among all configurations, the functionally graded BC-cubic lattice demonstrated the best overall structural efficiency, providing an optimal compromise between lightweight design, stress redistribution, controlled plastic deformation, and bird-strike resistance.