Out-of-plane energy absorption of 3D printed basalt-fiber-reinforced hierarchical honeycomb composite

• Vertex-based hierarchical triangular honeycomb structures are proposed. • Basalt-fiber-reinforced hierarchical honeycomb composites are additively manufactured. • Hierarchical order and triangular cell size significantly effect crushing properties. • Energy absorption of hierarchical triangular honeycombs is increased significantly. This work presents a new type of hierarchical triangular honeycomb created by iteratively replacing each vertex of conventional hexagonal cells with a smaller equilateral triangle. The combination of green and recyclable short basalt-fiber-reinforced composite with advanced additive manufacturing technology makes it possible to design and fabricate the 3D printed hierarchical triangular honeycomb composites with exceptional mechanical properties for energy absorption applications. Out-of-plane quasi-static compression tests were performed on the 3D printed hierarchical honeycomb composite to investigate the compressive response and deformation behaviour of hierarchical triangular honeycombs. Parametric studies were conducted using ABAQUS/Explicit finite element code to study the effects of structural hierarchy and triangular cell size on mechanical properties and energy absorption of 3D printed hierarchical triangular honeycombs. The result revealed that the 3D printed hierarchical triangular honeycomb composite experienced a large and stable plastic deformation to densification without fracture failure resulting in excellent energy absorption. The second level triangular honeycomb composite exhibited the most promising mechanical properties. After optimization of the triangular cell size, the mean crushing force and specific energy absorption of the second level triangular honeycomb composite were about 1.7 times and 2.0 times those of the conventional hexagonal honeycomb composite. Compared to other typical hierarchical honeycombs, the proposed hierarchical triangular honeycomb composite exhibited higher plateau stress and larger densification strain, thus providing some insights in designing lightweight, recyclable and sustainable 3D printed honeycomb composites with superior mechanical properties.