Multifunctional microtruss laminates: Textile synthesis and properties
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Open cell periodic metal truss structures can exhibit significantly higher stiffnesses and strengths than stochastic cellular metal structures of the same relative density while still providing high mechanical energy absorption and efficient heat exchange opportunities. Here, a potentially inexpensive textile-based approach to the synthesis of periodic metal microtruss laminates is reported. The process consists of selecting a wire weave, laying up the mesh and joining using a transient liquid phase. Example structures constructed from nichrome (Ni–24Fe–16Cr) wire cloth were made and tested. These exhibited a linear dependence of stiffness and strength upon relative density, absorbed large amounts of mechanical energy, and showed good potential for efficient heat exchange.
I. INTRODUCTION
Cellular solids are made up of interconnected networks of solid struts or plates which form the edges and faces of cells.1 Cellular solids based upon polymers are often used for thermal insulation, protective packaging, filtering, sandwich panel cores, or to provide buoyancy among many other applications.1 These types of materials can also be synthesized from metals. Cellular metals appear to possess useful combinations of thermophysical and mechanical properties that can be tailored by adjusting the relative density, cellular architecture, or metal type.2– 4 There is a growing interest in using cellular metals for applications where more than one function is required.2,3 For example, load supporting cellular metal structures might also simultaneously provide mechanical impact/blast absorption,5,6 thermal management,5,6 noise attenuation,5 catalyst support,5 filtration,5 electrical energy storage,7 retardation of chemical reactions and/or fire,5,8 or act as a host for the in-growth of biological tissue.9 The properties of a cellular metal depend upon both the topology of the metal and its properties. Several classes of cellular metals are emerging. One is stochastic in nature, based upon foaming.4 Another utilizes polymer or wax truss patterns and investment casting to create a periodic metal truss structure.10,11 Directional foaming results in architectures that are predominantly closed cell, often with wide distributions of cell size1 and many imperfections.12 Closed cell stochastic metal foams are used for sound attenuation and impact energy absorption.4 Open cell stochastic metal foams are made using reticulated polymer foams templates. In one approach, 890
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J. Mater. Res., Vol. 16, No. 3, Mar 2001 Downloaded: 14 Jan 2015
the template is used as a pattern for an investment casting mold which is then filled with a liquid metal and solidified.4 In other approaches, metal vapor or a fine metal powder slurry is deposited directly on to the template.13,14 In the latter, a subsequent heat treatment removes the organic compounds and densifies the structure. Open cell stochastic metal foams are used for lightweight heat exchangers and as the electrodes in nickel metal hydride batteries.4 Their Young’s m
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