Compressive collapse modes of hyperelastic origami honeycombs

Mechanical metamaterials are currently redefining the scope of achievable material properties through the use of micro-architecture. Origami-inspired metamaterials represent one avenue for design and optimisation of these materials, offering a large geometric design space with a range of unique and highly tunable properties. In this investigation, we consider the mechanics of flexible, elastic origami honeycombs with the “symmetric diamond Miura-ori” cell geometry. Potential applications for these materials include biomedical devices, wave attenuation, blast protection, energy absorption, soft robotics, deployable and reconfigurable structures, and many more. In this investigation, we develop insights into the large strain elastic compressive collapse mechanisms of these materials. A key question is to what extent the compressive collapse of these materials follows origami “rigid facet” folding kinematics to large strains, and whether or not that adherence is desirable for a given application. To answer this question, two modelling approaches are used. An analytical model is derived that predicts the large strain response adhering to folding kinematics, while a finite element (FE) model captures additional collapse mechanisms. Together, these modelling approaches are used to identify different regimes of collapse within the geometric design space, and create a design map quantifying this. The comparison also validates the analytical model within its regime of applicability, and provides an understanding of its accuracy outside of this. Following this, the new design map is applied to two case studies: the application of these materials as soft robotic actuators (where folding kinematics is desirable to large strains) and elastic energy absorbers (where departures from folding kinematics are shown to be advantageous). For the former regime, the hyperelastic analytical model derived here provides an accurate and computationally efficient route to exploit the rich material design space. • Finite strain crushing of hyperelastic origami honeycombs was studied using finite element (FE) simulations. • An analytical model capturing origami folding kinematics-dominant modes of collapse was derived and validated. • A map of collapse modes across the design space was developed highlighting three distinct regimes of collapse. • A discussion on practical considerations for the design and implementation of these materials is included.