Energy absorption characteristics of additively manufactured sea sponge-inspired lattice structures under low-velocity impact loading

Low-velocity impact tests are carried out to explore the energy absorption characteristics of bio-inspired lattices, mimicking the architecture of the marine sponge organism Euplectella aspergillum. These sea sponge-inspired lattice structures feature a square-grid 2D lattice with double diagonal bracings and are additively manufactured via digital light processing (DLP). The collapse strength and energy absorption capacity of sea sponge lattice structures are evaluated under various impact conditions and are compared to those of their constituent square-grid and double diagonal lattices. This study demonstrates that sea sponge lattices can achieve an 11-fold increase in energy absorption compared to the square-grid lattice, due to the stabilizing effect of the double diagonal bracings prompting the structure to collapse layer-by-layer under impact. By adjusting the thickness ratio in the sea sponge lattice, up to 76.7% increment in energy absorption is attained. It is also shown that sea-sponge lattices outperform well-established energy-absorbing materials of equal weight, such as hexagonal honeycombs, confirming their significant potential for impact mitigation. Additionally, this research highlights the enhancements in energy absorption achieved by adding a small amount (0.015 phr) of Multi-Walled Carbon Nanotubes (MWCNTs) to the photocurable resin, thus unlocking new possibilities for the design of innovative lightweight structures with multifunctional attributes.