Experimental and Numerical Studies of Additively Manufactured Metallic Origami-Inspired Metamaterials Under Impact

Abstract Origami-inspired cellular metamaterials provide a promising strategy for impact protection, as their collapse behaviour can be programmed through cell geometry and topology design. This study investigates the dynamic compressive response of three types of Miura-ori-based cellular metamaterials fabricated from 316L stainless steel by selective laser melting. These three designs include a straight-crease Miura-ori reference geometry, denoted as R, and two curved-crease derivatives, denoted as C and S. Impact experiments were performed using a forward direct impact Hopkinson bar at nominal impact velocities of 24 m/s and 53 m/s, with high-speed imaging used to identify the corresponding collapse mechanisms. Shell-based finite-element models were developed to examine the effects of loading conditions and material strain-rate sensitivity. Four finite element modelling strategies were compared: constant-velocity and initial-velocity loading, each with and without a Johnson–Cook strain-rate-dependent constitutive model. Additional quasi-static and 55 m/s constant-velocity simulations were conducted on specimens of R-cube, C-cube, and S-cube configurations to assess the effective material-level response of these three geometric types. The finite element results show that the dynamic loading condition has little influence on the predicted stress–strain response, whereas strain-rate sensitivity is essential for reproducing the experimentally measured dynamic strengthening. The rate-independent models substantially under-predict the crushing stress, while the rate-dependent models capture both the plateau stress and the main collapse behaviours with good accuracy. The experimental and numerical results also demonstrate that curved-crease design and rate-sensitive material modelling are both critical for optimising and predicting the impact response of additively manufactured origami-inspired metallic metamaterials.