Mechanical Properties of Internally Hierarchical Multiphase Lattices Inspired by Precipitation Strengthening Mechanisms

Multi-Physical Lattice Metamaterials Enabled by Additive Manufacturing: Design Principles, Interaction Mechanisms, and Multifunctional Applications

Lattice metamaterials emerge as advanced architected materials with superior physical properties and significant potential for lightweight applications. Recent developments in additive manufacturing (AM) techniques facilitate the manufacturing of lattice metamaterials with intricate microarchitectures and promote their applications in multi-physical scenarios. Previous reviews on lattice metamaterials have largely focused on a specific/single physical field, with limited discussion on their multi-physical properties, interaction mechanisms, and multifunctional applications. Accordingly, this article critically reviews the design principles, structure-mechanism-property relationships, interaction mechanisms, and multifunctional applications of multi-physical lattice metamaterials enabled by AM techniques. First, lattice metamaterials are categorized into homogeneous lattices, inhomogeneous lattices, and other forms, whose design principles and AM processes are critically discussed, including the benefits and drawbacks of different AM techniques for fabricating different types of lattices. Subsequently, the structure-mechanism-property relationships and interaction mechanisms of lattice metamaterials in a range of physical fields, including mechanical, acoustic, electromagnetic/optical, and thermal disciplines, are summarized to reveal critical design principles. Moreover, the multifunctional applications of lattice metamaterials, such as sound absorbers, insulators, and manipulators, sensors, actuators, and soft robots, thermal management, invisible cloaks, and biomedical implants, are enumerated. These design principles and structure-mechanism-property relationships provide effective design guidelines for lattice metamaterials in multifunctional applications.

Superior Strength, Toughness, and Damage-Tolerance Observed in Microlattices of Aperiodic Unit Cells

Characterized by periodic cellular unit cells, microlattices offer exceptional potential as lightweight and robust materials. However, their inherent periodicity poses the risk of catastrophic global failure. To address this limitation, a novel approach, that is to introduce microlattices composed of aperiodic unit cells inspired by Einstein's tile, where the orientation of cells never repeats in the same orientation is proposed. Experiments and simulations are conducted to validate the concept by comparing compressive responses of the aperiodic microlattices with those of common periodic microlattices. Indeed, the microlattices exhibit stable and progressive compressive deformation, contrasting with catastrophic fracture of periodic structures. At the same relative density, the microlattices outperform the periodic ones, exhibiting fracture strain, energy absorption, crushing stress efficiency, and smoothness coefficients at least 830%, 300%, 130%, and 160% higher, respectively. These improvements can be attributed to aperiodicity, where diverse failure thresholds exist locally due to varying strut angles and contact modes during compression. This effectively prevents both global fracture and abrupt stress drops. Furthermore, the aperiodic microlattice exhibits good damage tolerance with excellent deformation recoverability, retaining 76% ultimate stress post-recovery at 30% compressive strain. Overall, a novel concept of adopting aperiodic cell arrangements to achieve damage-tolerant microlattice metamaterials is presented.

Suture Interface Inspired Self-Recovery Architected Structures for Reusable Energy Absorption

Designing materials and structures with high energy absorption and self-recoverability remains a challenge for reusable energy absorption, particularly in aerospace engineering applications (i.e., planetary landers). While the prevalent design methods of reusable energy absorbers mainly use the mechanical instability of tilted and curved beams, the limited energy absorption capabilities and low strength of tilted or curved beams limit performance improvement. In nature, Phlorodes diabolicus has evolved extreme impact resistance, in which the suture interface structure plays a key role. Herein, we propose a convex interface slide design strategy for reusability and energy absorption through friction interface, geometry, and bending elasticity, inspired by the elytra of Phlorodes diabolicus. Convex interfaces slide to achieve a more than 270% higher energy absorption capacity per unit volume than the curved beams. The convex interface slide design can be easily integrated with other structures to achieve multiple functions, such as various shapes and self-recoverability. Furthermore, we developed a theoretical model to predict the mechanical behavior and energy absorption performance. Our strategy opens up a new design space for creating reusable energy-absorbing structures.