Microarchitectured cellular solids - the hunt for statically determinate periodic trusses (original) (raw)
Related papers
Study of architectural responses of 3D periodic cellular materials
Modelling and Simulation in Materials Science and Engineering, 2013
The functional properties of periodic cellular solids such as photonic and phononic crystals, nanocrystal superlattices and foams may be tuned by an applied inhomogeneous mechanical strain. A fundamental methodology to analyse the structure of periodic cellular materials is presented here and is compared directly with indentation experiments on three-dimensional microframed polymer photonic crystals. The application of single-continuumscale finite-element modelling (FEM) was impossible due to the numerous cells involved and the intricate continuum geometry within each cell. However, a method of dual-scale FEM was implemented to provide stress and displacement values on both scales by applying an upper scale continuum FEM with reference to the lower scale continuum FEM to provide coarse-grained stressstrain relationships. Architecture and orientation dependences of the periodic porous materials on the macro-/microscopic responses were investigated under different loading conditions. Our study revealed a computational tool for exploring elastic strain engineering of photonic crystals and, more broadly, may help the design of metamaterials with mechanical controllability.
Fabrication and structural performance of periodic cellular metal sandwich structures
Composites Science and Technology, 2003
Metallic sandwich panels with periodic, open-cell cores are important new structures, enabled by novel fabrication and topology design tools. Fabrication protocols based on the sheet forming of trusses and shell elements (egg-boxes) as well as textile assembly have allowed the manufacture of robust structures by inexpensive routes. Topology optimization enables control of failure mechanisms at the truss length scale, leading to superior structural performance. Analysis, testing and optimization have demonstrated that sandwich panels constructed with these cores sustain loads at much lower relative densities than stochastic foams. Moreover, the peak strengths of truss and textile cores are superior to honeycombs at low relative densities, because of their superior buckling resistance. Additional benefits of the truss/textile cores over honeycombs reside in their potentially lower manufacturing cost as well as in their multifunctionality.
Stiffness and strength of tridimensional periodic lattices
Computer methods in applied mechanics and …, 2012
This paper presents a method for the linear analysis of the stiffness and strength of open and closed cell lattices with arbitrary topology. The method hinges on a multiscale approach that separates the analysis of the lattice in two scales. At the macroscopic level, the lattice is considered as a uniform material; at the microscopic scale, on the other hand, the cell microstructure is modelled in detail by means of an in-house finite element solver. The method allows determine the macroscopic stiffness, the internal forces in the edges and walls of the lattice, as well as the global periodic buckling loads, along with their buckling modes. Four cube-based lattices and nine cell topologies derived by Archimedean polyhedra are studied. Several of them are characterized here for the first time with a particular attention on the role that the cell wall plays on the stiffness and strength properties. The method, automated in a computational routine, has been used to develop material property charts that help to gain insight into the performance of the lattices under investigation.► We present a multiscale procedure for the analysis of tridimensional lattices. ► The procedure can handle both open and closed cell lattices. ► We determine stiffness, buckling and yield strength for arbitrary lattice. ► Material property charts are produced and 13 different topologies are compared. ► Eight topologies have been characterized for the first time.
Shape Design of Periodic Cellular Materials Under Cyclic Loading
Volume 5: 37th Design Automation Conference, Parts A and B, 2011
A numerical method based on asymptotic homogenization theory is presented for the design of lattice materials against fatigue failure. The method is applied to study the effect of unit cell shape on the fatigue strength of hexagonal and square lattices. Cell shapes with regular and optimized geometry are examined. A unit cell is considered to possess a regular shape if the geometric primitives defining its inner boundaries are joined with an arc fillet, whose radius is 1% of the cell length. An optimized cell shape, on the other hand, is obtained by minimizing the curvature of its interior borders, which are conceived as continuous in curvature to smooth stress localization.
Journal of Sandwich Structures & Materials, 2012
The mechanical properties of micro-lattice structures made of interconnected metallic struts are calculated analytically, in order to derive their elastic modulus and Poisson’s ratio in the three Cartesian directions. The geometry of the investigated unit cell is a body centered cuboid, which is a more generic case of the well-known body centered cubic geometry. The Bernoulli–Euler and Timoshenko beam theories are used for the analytical solution of the unit cell response under complex loading. The derived elastic constants are compared to the relative numerical ones. The influence of geometrical parameters on the stiffness coefficients of the cellular structure is parametrically determined. The derived elasticity matrices are introduced in a homogenised numerical model of the core and its results are compared to a numerical model with explicit representation of the core geometry indicating an excellent accuracy, while the solution time is considerably reduced.
Effective properties of the octet-truss lattice material
Journal of the Mechanics and Physics of Solids, 2001
The e ective mechanical properties of the octet-truss lattice structured material have been investigated both experimentally and theoretically. Analytical and FE calculations of the elastic properties and plastic yielding collapse surfaces are reported. The intervention of elastic buckling of the struts is also analysed in an approximate manner. Good agreement is found between the predictions of the strength and experimental observations from tests on the octet-truss material made from a casting aluminium alloy. Moreover, the strength and sti ness of the octet-truss material are stretching-dominated and compare favourably with the corresponding properties of metallic foams. Thus, the octet-truss lattice material can be considered as a promising alternative to metallic foams in lightweight structures.