Active mechanical metamaterials (AMMs) (or smart mechanical metamaterials) that combine the configurations of mechanical metamaterials and the active control of stimuli‐responsive materials have been widely investigated in recent decades. The elaborate artificial microstructures of mechanical metamaterials and the stimulus response characteristics of smart materials both contribute to AMMs, making them achieve excellent properties beyond the conventional metamaterials. The micro and macro structures of the AMMs are designed based on structural construction principles such as, phase transition, strain mismatch, and mechanical instability. Considering the controllability and efficiency of the stimuli‐responsive materials, physical fields such as, the temperature, chemicals, light, electric current, magnetic field, and pressure have been adopted as the external stimuli in practice. In this paper, the frontier works and the latest progress in AMMs from the aspects of the mechanics and materials are reviewed. The functions and engineering applications of the AMMs are also discussed. Finally, existing issues and future perspectives in this field are briefly described. This review is expected to provide the basis and inspiration for the follow‐up research on AMMs.

Cellular ceramic structures (CCSs) are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties. Herein, the CCSs with different structural parameters, i.e., relative density, layer, size of unit cells, and structural configuration, were designed and prepared by digital light processing (DLP)-based additive manufacturing (AM) technology to investigate their responses under compressive loading systematically. It was demonstrated that as the relative density increased and the size of the unit cells decreased, the mechanical properties of one-layer CCSs increased. The mechanical properties of three-layer CCSs were more outstanding than those of the CCSs with one and two layers. In addition, structural configurations also played a vital role in the mechanical properties of the CCSs. Overall, the mechanical properties of the CCSs from superior to inferior were that with the structural configurations of modified body-centered cubic (MBCC), Octet, SchwarzP, IWP, and body-centered cubic (BCC). Furthermore, structural parameters also had significant impacts on the failure mode of the CCSs under compressive loading. As the relative density increased, the failure mode of the one-layer CCSs changed from parallel—vertical—inclined mode to parallel—vertical mode. It was worth noting that the size of the unit cells did not alter the failure mode. Inclined fracture took a greater proportion in the failure mode of the multi-layer CCSs. But it could be suppressed by the increased relative density. Similarly, the proportions of the parallel—vertical mode and the fracture along a specific plane always changed with the variation of the structural configurations. This study will serve as the base for investigating the mechanical properties of the CCSs.

Precursor-derived SiOC ceramic (PDC-SiOC) microlattices exhibit excellent oxidation resistance, high-temperature stability, as well as superior mechanical properties. However, the printing accuracy of PDC-SiOC microlattices by 3D printing is still limited, and the mechanical properties of PDC-SiOC microlattices have not been studied systematically. Here, PDC-SiOC octet microlattices were fabricated by projection micro stereolithography (PμSL) 3D printing, and photoabsorber (Sudan III) 's effect on accuracy was systematically analyzed. The results showed that the addition of Sudan III improved the printing accuracy significantly. Then the ceramization process of the green body was analyzed in detail. The order of the green body decreased and most of their chemical bonds were broken during pyrolysis. After that, PDC-SiOC microlattices with different truss diameters in the 52-220 μm range were fabricated and their mechanical properties were investigated. The PDC-SiOC microlattices with 52 μm truss diameter exhibited a higher compression strength (31 MPa) than those with bigger truss diameters. The size effect among PDC-SiOC microlattices was analyzed. Our work provides a deeper insight into the manufacturing of PDC-SiOC micro-scaled architectures by 3D printing and paves a path to the research of size effect in ceramic structures.

Ceramic lattice structures (CLSs) are promising candidates for structural applications used in conventional and extreme environments because of their extraordinary properties. Herein, CLSs with different structural configurations, including body-centred cubic (BCC), Octet, and modified body-centred cubic (MBCC), were designed and fabricated by digital light processing (DLP)-based additive manufacturing technology to explore their quasi-static and dynamic compressive behaviours. It was demonstrated that when relative density was a constant, quasi-static compressive strength (QS), quasi-static Young’s modulus (QY), and quasi-static energy absorption (QE) of CLSs with an MBCC structural configuration were the best, Octet ranked secondly, BCC was the poorest. The same thing happened on dynamic mechanical properties of CLSs. Increasing the relative density from 20% to 40% dramatically improved the QS, QY, and QE of CLSs. Furthermore, it was revealed by experiment and simulation that the quasi-static failure mode of CLSs changed from partially fracture along a specific plane to integrally fracture at most nodes as relative density increased. Furthermore, the dynamical mechanical properties of CLSs were significantly outstanding than quasi-static mechanical properties due to the strain-rate effect. This study provides a new basis for further study on tailoring the mechanical properties of CLSs.