Mechanical behaviour of gel-filled additively-manufactured lattice structures under quasi-static compressive loading

The worldwide incidence of traumatic brain injuries (TBIs) is on the rise. Helmets are one of the best technologies available to prevent TBIs from impacts to the head during recreational and occupational activities. The most commonly used material for helmet liners is expanded polystyrene (EPS) foam. However, while EPS can reduce linear accelerations from impacts, it does not perform as well at reducing rotational accelerations which are considered to be the most harmful to brain tissue. Recently, prismatic lattice structures have shown promise in reducing these harmful rotational accelerations. Here, a new structure for energy dissipation applications is presented that is hypothesised to improve the energy dissipation of the prismatic lattice by filling it with a gel. To test this hypothesis, 3D printed prismatic lattices fabricated from PLA, PET-G, and ABS were filled with 5 wt% and 10 wt% agar and tested to failure under quasi-static compression. Compared to the unfilled control group, it was found that PLA lattices filled with 10 wt% agar had the best performance demonstrating a 46.1% increase in energy absorbed and 57.4% increase in displacement to failure. These results demonstrate the superior energy dissipation properties of gel-filled prismatic lattices compared to unfilled prismatic lattices during quasi-static compression.