3D‐Printed Soft and Hard Meta‐Structures with Supreme Energy Absorption and Dissipation Capacities in Cyclic Loading Conditions

The main objective of this article is to introduce novel 3D bio‐inspired auxetic meta‐structures printed with soft/hard polymers for energy absorption/dissipation applications under single and cyclic loading–unloading. Meta‐structures are developed based on understanding the hyper‐elastic feature of thermoplastic polyurethane (TPU) polymers, elastoplastic behavior of polyamide 12 (PA 12), and snowflake inspired design, derived from theory and experiments. The 3D meta‐structures are fabricated by multi‐jet fusion 3D printing technology. The feasibility and mechanical performance of different meta‐structures are assessed experimentally and numerically. Computational finite element models (FEMs) for the meta‐structures are developed and verified by the experiments. Mechanical compression tests on TPU auxetics show unique features like large recoverable deformations, stress softening, mechanical hysteresis characterized by non‐coincident compressive loading–unloading curve, Mullins effect, cyclic stress softening, and high energy absorption/dissipation capacity. Mechanical testing on PA 12 meta‐structures also reveals their elastoplastic behavior with residual strains and high energy absorption/dissipation performance. It is shown that the developed FEMs can replicate the main features observed in the experiments with a high accuracy. The material‐structural model, conceptual design, and results are expected to be instrumental in 3D printing tunable soft and hard meta‐devices with high energy absorption/dissipation features for applications like lightweight drones and unmanned aerial vehicles (UAVs).