Mechanisms-based dual-phase metamaterials: Exploiting rotational deformation for enhanced energy absorption

Heterogeneous metamaterials inherently introduce deformation discontinuities that can trigger localized rotational motions. However, effectively exploiting such rotation for enhanced energy absorption remains challenging, as it is typically passive and kinematically unconstrained. In this work, a mechanism-based architecture is proposed by integrating kirigami-inspired features into dual-phase lattice metamaterials to actively guide and amplify rotational deformation. To elucidate the role of three-dimensional phase distribution, two spatial topologies—aligned and staggered—are systematically investigated. Quasi-static compression experiments on additively manufactured aligned stainless-steel specimens reveal a controllable rotational mechanism, leading to a characteristic two-stage response: a kirigami-dominated stage (K-Stage) followed by a lattice-dominated stage (L-Stage). Parametric finite element analyses show that the K-Stage kinematics are governed by the interplay between ligament thickness (t) and initial rotation angle (θ), resulting in four distinct deformation modes that critically influence energy absorption performance. A deformation-mode map is established to identify parameter regimes that ensure stable and controllable rotational behavior. Importantly, the K-Stage response is found to be insensitive to the stacking strategy, indicating that the rotation mechanism operates independently of the global phase arrangement. In contrast, the L-Stage behavior is strongly dependent on spatial topology. The staggered configuration forms a fully interconnected reinforcement network, effectively eliminating the directional anisotropy observed in the aligned structure and maximizing the strengthening potential of the dual-phase system. As a result, the optimized staggered lattice achieves a 60.7% increase in specific energy absorption compared to the baseline dual-phase lattice. These findings demonstrate that explicitly embedding rotational mechanisms within architecture-dominated systems provides a robust and material-efficient strategy for designing high-performance energy-absorbing structures.