Metal Foams: A Design Guide

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14 Metal Foams: A Design Guide cooling, the mold materials are removed leaving behind the metal equivalent of the original polymer foam. Metal powder slurries can also be used instead of liquid metals. These are subsequently sintered. The method gives open-cell foams with pore sizes of 1–5 mm and relative densities as low as 0.05. The process can be used to manufacture foams from almost any metal that can be investment cast. In a variant of the process, the precursor structure is assembled from injection-molded polymeric or wax lattices. The lattice structure is coated with a casting slurry and fired, burning it out and leaving a negative image mold. Metal is cast or pressure-cast into the mold using conventional investment casting techniques. 2.6 Metal deposition on cellular preforms Open-cell polymer foams can serve as templates upon which metals are deposited by chemical vapor decomposition (CVD), by evaporation or by electrodeposition. In the INCO process, nickel is deposited by the decomposition of nickel carbonyl, Ni⊲CO⊳4. Figure 2.6 schematically illustrates one approach in which an open-cell polymer is placed in a CVD reactor and nickel carbonyl is introduced. This gas decomposes to nickel and carbon monoxide at a temperature of about 100°C and coats all the exposed heated surfaces within the reactor. Infrared or RF heating can be used to heat only the polymer foam. After several tens of micrometers of the metal have been deposited, the metal-coated polymer foam is removed from the CVD reactor and the polymer is burnt out by heating in air. This results in a cellular metal structure with hollow ligaments. A subsequent sintering step is used to densify the ligaments. Nickel carbonyl gas is highly toxic and requires costly environmental controls before it can be used for manufacturing nickel foams. Some countries, such as the United States, have effectively banned its use and others make it prohibitively expensive to implement industrial processes that utilize nickel carbonyl gas. Electro- or electroless deposition methods have also been used to coat the preforms, but the nickel deposited by the CVD technique has a lower electrical resistance than that created by other methods. The pore size can be varied over a wide range. Foams with open pore sizes in the 100–300 µm diameter range are available. The method is restricted to pure elements such as nickel or titanium because of the difficulty of CVD or electrodeposition of alloys. It gives the lowest relative density (0.02–0.05) foams available today. 2.7 Entrapped gas expansion The solubility in metals of inert gases like argon is very low. Powder metallurgy techniques have been developed to manufacture materials with a dispersion of small pores containing an inert gas at a high pressure. When these
a) Vapor deposition of Nickel b) Burnout polymer Ni(CO) 4 c) Sinter (Ligament densification) METAL DEPOSITION ON CELLULAR PREFORM Vacuum Open cell polymer foam polymer ligaments Heater Thermally decomposable Nickel containing gas Vacuum pump Nickel deposit Hollow Nickel ligaments Heater Collapsed (dense) ligaments Heater Making metal foams 15 Figure 2.6 Schematic illustration of the CVD process used to create open-cell nickel foams (INCO process)
Page 1 and 2: Metal Foams: A Design Guide
Page 3 and 4: Copyright © 2000 by Butterworth-He
Page 5 and 6: vi Contents 4.3 Foam property chart
Page 7 and 8: viii Contents 17 Case studies 217 1
Page 9 and 10: List of contributors M.F. Ashby Cam
Page 11 and 12: Table of physical constants and con
Page 13 and 14: Chapter 1 Introduction Metal foams
Page 15 and 16: Activity Research Industrial take-u
Page 17 and 18: Application Comment Introduction Bi
Page 19 and 20: Cell size (cm) Making metal foams 7
Page 21 and 22: Making metal foams solidify. The th
Page 23 and 24: Making metal foams 11 2.4 Gas-relea
Page 25: a) Preform Polymer ligaments d) Rem
Page 29 and 30: Process Steps a) Powder / Can prepa
Page 31 and 32: Making metal foams 19 flight in a t
Page 33 and 34: a) Metal - Hydrogen binary phase di
Page 35 and 36: Entrapped gas expansion Making meta
Page 37 and 38: (a) (b) (c) 100µm Characterization
Page 39 and 40: E/E bulk σ peak /σ bulk 1.2 1.0 0
Page 41 and 42: Stress (MPa) Characterization metho
Page 43 and 44: Characterization methods 31 foam sp
Page 45 and 46: Characterization methods 33 ž Prop
Page 47 and 48: F/2 F/2 F/2 F/2 τ Core Characteriz
Page 49 and 50: Characterization methods 37 40 40 4
Page 51 and 52: Characterization methods 39 Gioux,
Page 53 and 54: (a) (b) (c) Properties of metal foa
Page 55 and 56: Table 4.1 (a) Ranges a for mechanic
Page 57 and 58: Stress, σ Schematic Young's modulu
Page 59 and 60: Properties of metal foams 47 foams.
Page 61 and 62: Properties of metal foams 49 show t
Page 63 and 64: Modulus 0.5 /Density (GPa 0.5 /(Mg/
Page 65 and 66: elations take the form P Ł � Ł
Page 67 and 68: Chapter 5 Design analysis for mater
Page 69 and 70: Table 5.1 Design requirements Desig
Page 71 and 72: Design analysis for material select
Page 73 and 74: 5.4 Where might metal foams excel?
Page 75 and 76: Table 6.1 Constitutive equations fo
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h SECTION h o h i d d o a b ;;; QQQ
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6.3 Elastic deflection of beams and
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6.4 Failure of beams and panels (a)
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;; ;;; ;; M ;; ;;; ;; ;;; ;; ;; ;;
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Torsion of shafts T T,q T T,q Yield
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R a 2 Flow field R F R 2a 2 F F s c
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;; ; QQ Q ¢¢ ¢ ;; ;; QQ QQ ¢¢
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; ;; Creep p e p e • Area A u F 2
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and its deviatoric (i.e. shear) com
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Normalized effective stress 1.4 1.2
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A constitutive model for metal foam
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A constitutive model for metal foam
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Stress amplitude, ∆σ + Stress,
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Axial strain (%) 5 4 3 2 1 0 0 σma
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Nominal compressive strain Nominal
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σ max σ pl τ max τ pl σ max σ
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Design for fatigue with metal foams
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the net section stress criterion re
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E σ pl (m) 10 1 0.1 0.01 0.1 Relat
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Chapter 9 Design for creep with met
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Design for creep with metal foams 1
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instead to: � Pε 3 D Pε0 2 s Ł
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Time to failure (hours) 10 2 10 1 1
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Design for creep with metal foams 1
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Chapter 10 Sandwich structures Sand
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Sandwich structures 115 The elastic
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Indentation Sandwich structures 117
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H H Core shear Core shear Collapse
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0.5 10−1 t c t c 10 −2 0.5 10
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Sandwich structures 123 the contact
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Sandwich structures 125 four sectio
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c t p p Figure 10.9 Sandwich panel
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Sandwich structures 129 with k ¾ D
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c/ Face sheet yielding 0.14 0.12 0.
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Weight index, ψ 10 −1 10 −2 10
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Sandwich structures 135 To construc
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Sandwich structures 137 The associa
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Sandwich structures 139 Note that,
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where D � 2⊲1 Eft 2 f ⊳GcR Sa
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Weight index ψ = W/2πR 2 ρ s W c
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Sandwich structures 145 plastic yie
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Sandwich structures 147 within the
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Sandwich structures 149 Shuaeib, F.
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Energy management: packaging and bl
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Energy/Unit cost (kJ/£) 10 1 0.1 0
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ys crushes axially at the load Ener
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peak pressure MPa Impulse/(mass of
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Chapter 12 Sound absorption and vib
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Sound absorption and vibration supp
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0 Sound absorption and vibration su
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Chapter 13 Thermal management and h
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Thermal management and heat transfe
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Thermal management and heat transfe
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~ P ~ Re 2.6 1000 800 600 400 200 0
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Chapter 14 Electrical properties of
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Electrical properties of metal foam
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Electrical properties of metal foam
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15.3 Joining of metal foams Cutting
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Pull-out load, F p (N) 10 5 10 4 10
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Cyclic loading of fasteners Cutting
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Time, material, energy, capital, in
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Cost estimation and viability 203 A
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$/Unit Melting Schematic of the liq
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Performance metric, P2 B Non-domina
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Cost estimation and viability 209 t
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Cost estimation and viability 211 i
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P 2 = 1/Loss coefficient (−) 1000
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Cost estimation and viability 215 C
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Chapter 17 Case studies Metal foams
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Case studies 219 Figure 17.2 A pres
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Case studies 221 Figure 17.4 Highwa
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Case studies 223 Figure 17.6 DUOCEL
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Case studies 225 density and high t
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Case studies 227 required for compa
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Maximum power density at electronic
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q *(MW/m 2) 15 10 Power density fix
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Case studies 233 which optimized sk
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e-mail: cymat@ican.net Web: www.cym
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Tel: C0043 7722 801-2125 Fax: C0043
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Chapter 19 Web sites An increasing
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http://www.seac.nl/english/recemat/
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(b) (continued) Appendix: Catalogue
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(f) Vibration-limited design Append
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Index (Company and trade names are
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Heat transfer 4, 182 Heat transfer
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Surface strain mapping 36 Syntactic
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Metal Foams: A Design Guide

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