A flexible design framework for lattice-based chiral mechanical metamaterials considering dynamic energy absorption

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While chiral mechanical metamaterials (CMMs) are reported promising in energy absorption due to the unique chiral effect, the energy-absorbing CMMs lack effective and generalized design methodologies and corresponding structure-property relationship studies. To this end, a design framework for lattice-based CMMs was proposed, and the dynamic compressive behaviors of CMMs were systematically investigated. Firstly, based on a predefined design baseline that considered a support-free metal additive manufacturing process, a screw-theory-based assembly rule was presented, which enabled the scalable twist effects and the characterization of chiral features. Secondly, an aperiodic design process that sequentially defines joints, strut connections, and geometrical features was proposed. This framework via parameterization enables the rapid generation of geometric and finite element models that contain a large number of unit cells. It also enables the integration of joint enhancement design, bio-inspired helical design, and gradient design. Finally, by finite element analysis and experiments of uniaxial medium-strain-rate (50 s−1) compression, the effects of chirality on mechanical properties (compressive strength, yield plateau, energy absorption, etc.) during the nonlinear large-deformation responses were elucidated. Results show that a comprehensive and flexible method is presented by independently defining each rod component or joint of the lattice type metamaterials, which enables the design from chiral to achiral, from rectangular to helical, and from uniform to gradient. The bidirectional gradient CMMs design along the axial and radial directions achieves a 52.0 % specific energy absorption enhancement compared with achiral lattices, demonstrating the energy absorption advantage of CMMs, and laying the foundation for further optimization, inverse design, and engineering applications.