Cellular metal lattices with hollow trusses

Cellular metal lattice truss structures are being investigated for use as multifunctional load supporting structures where their other functionalities include thermal management, dynamic load protection and acoustic damping. A simple method for making lattice structures with either solid or hollow trusses is reported. The approach involves laying up collinear arrays of either solid wires or hollow cylinders and then alternating the direction of successive layers. The alternating collinear assembly is metallically bonded by a brazing process. The dimensions of the cylinders, the wall thickness of hollow truss structures and the spacing between the trusses enable independent control of the cell size and the relative density of the structure. The process has been used to create stainless steel lattices with either square or diamond topologies with relative densities from 0.03 to 0.23. The through thickness elastic modulus of these lattice truss structures is found to be proportional to relative density. The square topology has twice the stiffness of the diamond oriented trusses. The peak compressive strengths of both topologies are similar and is controlled by plastic buckling. The structural efficiency of hollow truss structures with a fixed cell size is approximately proportional to the relative density unlike equivalent structures made from solid trusses whose peak strength has been predicted to scale with the cube of the relative density. The experimental data for hollow trusses lie between predictions for trusses with built-in and pin-jointed nodes consistent with experimental observations of constrained node rotation. The use of hollow trusses increases the resistance to buckling offsetting the usually rapid drop in strength as the relative density decreases in cellular systems where truss buckling controls failure. The low relative density hollow truss structures reported here have the highest reported specific peak strength of any cellular metal reported to date.

[1]  Haydn N. G. Wadley,et al.  Cellular Metal Truss Core Sandwich Structures , 2002 .

[2]  M. Ashby,et al.  The topological design of multifunctional cellular metals , 2001 .

[3]  Michael F. Ashby,et al.  Multifunctionality of cellular metal systems , 1998 .

[4]  Lorna J. Gibson,et al.  Defect sensitivity of a 3D truss material , 2001 .

[5]  R. Plunkett,et al.  Formulas for Stress and Strain , 1965 .

[6]  Lorna J. Gibson,et al.  Mechanical Behavior of Metallic Foams , 2000 .

[7]  Mustafa Güden,et al.  Crushing of aluminum closed cell foams: density and strain rate effects , 2000 .

[8]  T. Lu,et al.  Sound absorption in metallic foams , 1999 .

[9]  T. Lu,et al.  Thermal radiation in ultralight metal foams with open cells , 2004 .

[10]  U. Ramamurty,et al.  Strain rate sensitivity of a closed-cell aluminum foam , 2000 .

[11]  John W. Hutchinson,et al.  Optimal truss plates , 2001 .

[12]  N. Fleck,et al.  Collapse of truss core sandwich beams in 3-point bending , 2001 .

[13]  S. Torquato,et al.  Simulated Properties of Kagomé and Tetragonal Truss Core Panels , 2003 .

[14]  Hilary Bart-Smith,et al.  Influence of imperfections on the performance of metal foam core sandwich panels , 2002 .

[15]  T. Lu,et al.  Heat transfer in open-cell metal foams , 1998 .

[16]  Lorna J. Gibson,et al.  Modelling the mechanical behavior of cellular materials , 1989 .

[17]  D. Poulikakos,et al.  On the effective thermal conductivity of a three-dimensionally structured fluid-saturated metal foam , 2001 .

[18]  J. Banhart.  Manufacture, characterisation and application of cellular metals and metal foams , 2001 .

[19]  John W. Hutchinson,et al.  Performance of sandwich plates with truss cores , 2004 .

[20]  Joseph R. Davis,et al.  Properties and selection : irons, steels, and high-performance alloys , 1995 .

[21]  Michael F. Ashby,et al.  Cellular metals and metal foaming technology , 2001 .

[22]  Frank W. Zok,et al.  Design of metallic textile core sandwich panels , 2003 .

[23]  Michael F. Ashby,et al.  The mechanical properties of cellular solids , 1983 .

[24]  N. K. Anand,et al.  Use of porous baffles to enhance heat transfer in a rectangular channel , 2003 .

[25]  James Lankford,et al.  High strain rate compression of closed-cell aluminium foams , 2000 .

[26]  R. Mahajan,et al.  Forced Convection in High Porosity Metal Foams , 2000 .

[27]  Pranav Shrotriya,et al.  On the deformation of aluminum lattice block structures: from struts to structures , 2004 .

[28]  Y. Sugimura.  Mechanical response of single-layer tetrahedral trusses under shear loading , 2004 .

[29]  Haydn N. G. Wadley,et al.  On the performance of truss panels with Kagomé cores , 2003 .

[30]  Howard P. Hodson,et al.  The temperature dependence of effective thermal conductivity of open-celled steel alloy foams , 2004 .

[31]  Norman A. Fleck,et al.  Fabrication and structural performance of periodic cellular metal sandwich structures , 2003 .

[32]  N. Fleck,et al.  The out-of-plane compressive behaviour of woven-core sandwich plates , 2004 .

[33]  N. Fleck,et al.  High strain rate compressive behaviour of aluminium alloy foams , 2000 .

[34]  Hilary Bart-Smith,et al.  Measurement and analysis of the structural performance of cellular metal sandwich construction , 2001 .

[35]  Douglas T. Queheillalt,et al.  The effects of topology upon fluid-flow and heat-transfer within cellular copper structures , 2004 .

[36]  N. Fleck,et al.  The plastic collapse of sandwich beams with a metallic foam core , 2001 .

[37]  H. Wadley,et al.  Multifunctional microtruss laminates: Textile synthesis and properties , 2001 .

[38]  Dimos Poulikakos,et al.  Metal foams as compact high performance heat exchangers , 2003 .

[39]  Stefanie Chiras,et al.  The structural performance of near-optimized truss core panels , 2002 .

[40]  Ronald E. Miller,et al.  Failure of sandwich beams with metallic foam cores , 2001 .

[41]  Lorna J. Gibson,et al.  Mechanical behavior of a three-dimensional truss material , 2001 .

[42]  B. Kang,et al.  Forced convection from aluminum foam materials in an asymmetrically heated channel , 2001 .

[43]  T. Lu,et al.  Optimized acoustic properties of cellular solids , 1999 .

[44]  R. Mahajan,et al.  Thermophysical properties of high porosity metal foams , 2002 .

[45]  M. Ashby,et al.  Effective properties of the octet-truss lattice material , 2001 .

[46]  Abdulmalik A. Alghamdi,et al.  Collapsible impact energy absorbers: an overview , 2001 .

[47]  Wu Jie-jun,et al.  Damping and sound absorption properties of particle reinforced Al matrix composite foams , 2003 .