TY - JOUR

T1 - Functional mechanical metamaterial with independently tunable stiffness in the three spatial directions

AU - Fleisch, M.

AU - Thalhamer, A.

AU - Meier, G.

AU - Raguž, I.

AU - Fuchs, P. F.

AU - Pinter, G.

AU - Schlögl, S.

AU - Berer, M.

N1 - Publisher Copyright: © 2021 The Authors

PY - 2021/9

Y1 - 2021/9

N2 - Mechanical metamaterials with variable stiffness recently gained a lot of research interest, as they allow for structures with complex boundary and load conditions. Herein, we highlight the design, additive manufacturing, and mechanical testing of a new kind of bending-dominated metamaterial. By advancing from well-established mechanical metamaterials, the proposed geometry allows for varying the stiffness in the three spatial directions independently. Therefore, structures with different orientational properties can be designed, ranging from isotropic to anisotropic structures, including orthotropic structures. The compression modulus can be varied in the range of several orders of magnitude. Gradual transitions from one unit cell to the next can be realized, enabling smooth transitions from soft to hard regions. Specimens have been additively manufactured with acrylic resins and polylactic acid using Digital Light Processing and Fused Filament Fabrication, respectively. Two different numerical models have been employed using ABAQUS to describe the mechanical properties of the structure and verified by the experiments. Compression tests were performed to investigate the linear elastic properties of isotropic structures. Numerical models, based on three-point-bending test data, have been employed to study orthotropic structures. Compression test results for orthotropic and anisotropic structures are shown to highlight the independent variability. The manufacturing of the structures is not limited to the presented techniques and materials but can be expanded to all available additive manufacturing techniques and their respective materials. For a video of the compression tests of a specimen with three different compression moduli along the spatial axes, see the Supplementary Data available online.

AB - Mechanical metamaterials with variable stiffness recently gained a lot of research interest, as they allow for structures with complex boundary and load conditions. Herein, we highlight the design, additive manufacturing, and mechanical testing of a new kind of bending-dominated metamaterial. By advancing from well-established mechanical metamaterials, the proposed geometry allows for varying the stiffness in the three spatial directions independently. Therefore, structures with different orientational properties can be designed, ranging from isotropic to anisotropic structures, including orthotropic structures. The compression modulus can be varied in the range of several orders of magnitude. Gradual transitions from one unit cell to the next can be realized, enabling smooth transitions from soft to hard regions. Specimens have been additively manufactured with acrylic resins and polylactic acid using Digital Light Processing and Fused Filament Fabrication, respectively. Two different numerical models have been employed using ABAQUS to describe the mechanical properties of the structure and verified by the experiments. Compression tests were performed to investigate the linear elastic properties of isotropic structures. Numerical models, based on three-point-bending test data, have been employed to study orthotropic structures. Compression test results for orthotropic and anisotropic structures are shown to highlight the independent variability. The manufacturing of the structures is not limited to the presented techniques and materials but can be expanded to all available additive manufacturing techniques and their respective materials. For a video of the compression tests of a specimen with three different compression moduli along the spatial axes, see the Supplementary Data available online.

KW - Additive manufacturing

KW - Design

KW - Mechanical testing

KW - Neural network

KW - Numerical

UR - http://www.scopus.com/inward/record.url?scp=85110673172&partnerID=8YFLogxK

U2 - 10.1016/j.mtadv.2021.100155

DO - 10.1016/j.mtadv.2021.100155

M3 - Article

AN - SCOPUS:85110673172

VL - 11.2021

JO - Materials today advances

JF - Materials today advances

SN - 2590-0498

IS - September

M1 - 100155

ER -