Elastically-isotropic truss lattice materials of reduced plastic anisotropy

The elastically-anisotropic octet truss lattice exhibits high specific stiffness due to its stretching-dominated mechanical behavior. Here, elastically-isotropic truss lattices are designed in a way that the constituent beams respond in a stretching-dominated manner instead of bending. Topology cons...

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Bibliographic Details
Published inInternational journal of solids and structures Vol. 138; pp. 24 - 39
Main Authors Tancogne-Dejean, Thomas, Mohr, Dirk
Format Journal Article
LanguageEnglish
Published New York Elsevier Ltd 01.05.2018
Elsevier BV
Subjects
Additive manufacturing
Anisotropy
Body centered cubic lattice
Composition
Face centered cubic lattice
Isotropy
Lattices
Lithography
Mechanical properties
Metamaterial
Modulus of elasticity
Plastic anisotropy
Plasticity
Stiffness
Stretching
Superplasticity
Truss lattice
Yield strength
Yield stress
Isotropy
Truss lattice
Metamaterial
Plasticity
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Summary:The elastically-anisotropic octet truss lattice exhibits high specific stiffness due to its stretching-dominated mechanical behavior. Here, elastically-isotropic truss lattices are designed in a way that the constituent beams respond in a stretching-dominated manner instead of bending. Topology constraints ensuring an isotropic elastic response at the macroscopic level are derived from a detailed theoretical analysis of generic periodic truss structures. Specific elastically-isotropic structures are designed by combining elementary cubic truss lattices including the Simple Cubic (SC), Body-Centered Cubic (BCC) and Face-Centered Cubic (FCC) lattices. It is shown through periodic homogenization that these isotropic truss lattice compositions exhibit less initial yield anisotropy than the octet truss lattice. For example, the ratio of maximum to minimum yield stress of an SC-BCC-FCC truss lattice composition is 1.4 as compared to 2 for the octet truss lattice. Computational unit cell analysis is carried out to confirm the analytical Young's modulus and yield stress estimates. Selected isotropic structures of 20% relative density are built from a photopolymer using stereolithography. The Young's modulus and Poison's ratio measurements on specimens with different lattice orientations confirm the validity of the design constraints. In addition, the trends regarding the plastic anisotropy are confirmed by the experimental results.
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ISSN:0020-7683
1879-2146
DOI:10.1016/j.ijsolstr.2017.12.025