3D Printed Gyroid Lattices with Graded Density for Advanced Ballistic Protection

Additive manufacturing enables the fabrication of complex cellular architectures with controllable mechanical properties, making triple periodic minimum surface area (TPMS) networks promising candidates for lightweight, energy-absorbing applications. In this work, the mechanical response of 3D-printed polylactic acid (PLA) structures with gyroid filling was investigated under quasi-static compression and weight-drop impact. Three types of specimens with identical external dimensions (60 × 60 × 64mm) and comparable overall relative density (~26%) were fabricated: (i) uniform gyroid, (ii) a cell size graded variant, and (iii) a cell size graded variant plus wall. The relative density was experimentally verified by mass and geometric measurements, ensuring a fair comparison between the architectures. Mechanical tests focused on stress-strain behavior, stiffness, peak stress, and energy absorbed per unit volume. Impact tests were performed by free fall to evaluate the ability of each configuration to dissipate kinetic energy and to reveal possible sensitivity to strain rate. Particular attention was paid to the initiation and propagation of failure, as the studied architectures exhibit distinct collapse mechanisms. Preliminary observations suggest that functionally graded gyroid structures may provide better energy absorption compared to uniform grids. The motivation behind this research is the development of lightweight ballistic panels. Current ballistic protection systems are often limited by their high weight, which reduces mobility. By introducing grid structures based on gyroids with controlled relative density and functional grading, it is expected to achieve panels with reduced mass, while maintaining or improving energy absorption and impact resistance.