Impact performance enhancement of honeycombs through additive manufacturing-enabled geometrical tailoring

We report the enhanced low-velocity impact performance of geometrically tailored honeycomb structures enabled via stereolithography additive manufacturing. Geometrical tailoring of the honeycomb structures was realized by linearly varying the cell wall thickness along the through-thickness direction, while retaining the overall mass of the structures. We examine the effects of cell wall thickness gradient, impact energy, cell topology, geometric scaling and impact direction on the energy absorption capacity and damage mechanisms of tailored honeycombs. For the geometrical and material properties of honeycomb structures considered here, experimental results indicate that, at low impact energy levels (≤30 J), the effect of geometrical tailoring has no significant advantage. Nevertheless, at higher impact energy levels (>30 J), geometrically tailored honeycombs outperform non-tailored counterparts, exhibiting over 60% increase in energy absorption capacity. Experimental observations further reveal that geometrical tailoring results in a change of failure mode from brittle fracture to progressive damage of the cell walls from thinner sections at which the structures were subjected to low-velocity impact, offering superior energy absorption characteristics. The results of this study suggest that the concept of geometrical tailoring in conjunction with additive manufacturing offers new opportunities for the development of high performance architected lattices.