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© Fraunhofer IFAM
A look back and forward
Metal foams, the light-weight material of the future?
Dr.-Ing. Jörg Weise Fraunhofer IFAM, Bremen Germany
© Fraunhofer IFAM
Fraunhofer IFAM
Fraunhofer-Society
60 Institutes
20 000 employees
Annual turnover 2011
1,8 Mrd. Euro
München
Holzkirchen
Freiburg
Efringen- Kirchen
Freising Stuttgart
Pfinztal Karlsruhe Saarbrücken
St. Ingbert Kaiserslautern
Darmstadt Würzburg
Erlangen
Nürnberg
Ilmenau
Schkopau
Teltow
Oberhausen
Duisburg
Euskirchen Aachen St. Augustin
Schmallenberg
Dortmund
Potsdam Berlin
Rostock
Lübeck Itzehoe
Braunschweig
Hannover
Bremen
Bremerhaven
Jena
Leipzig
Chemnitz
Dresden
Cottbus
Magdeburg
Halle
Fürth
Wachtberg
Ettlingen
Kandern
Oldenburg
Freiberg
Paderborn
Kassel
Gießen Erfurt
Augsburg
Oberpfaffenhofen
Garching
Straubing
Bayreuth
Bronnbach
Prien
© Fraunhofer IFAM
Fraunhofer IFAM
Shaping and Functional Materials
Adhesive Bonding and Surfaces
Functional Structures Powder technology Sinter and composite
materials Cellular metallic materials Casting technology and
component development Biomaterial technology Materialography and
analytics Electrical powertrain systems Energy storage
Adhesive Bonding technology Adhesives and polymer
chemistry Applied surface and adhesion
science Plasma technology and
surfaces Paint and lacquer technology Assembly and processing of
CFC structures Training and technology
transfer
Prof. Matthias Busse Executive Director
Prof. Bernd Mayer Director
München
Holzkirchen
Freiburg
Efringen- Kirchen
Freising Stuttgart
Pfinztal Karlsruhe Saarbrücken
St. Ingbert Kaiserslautern
Darmstadt Würzburg
Erlangen
Nürnberg
Ilmenau
Schkopau
Teltow
Oberhausen
Duisburg
Euskirchen Aachen St. Augustin
Schmallenberg
Dortmund
Potsdam Berlin
Rostock
Lübeck Itzehoe
Braunschweig
Hannover
Bremen
Bremerhaven
Jena
Leipzig
Chemnitz
Dresden
Cottbus Magdeburg
Halle
Fürth
Wachtberg
Ettlingen
Kandern
Oldenburg
Freiberg
Paderborn
Kassel
Gießen Erfurt
Augsburg
Oberpfaffenhofen
Garching
Straubing
Bayreuth
Bronnbach
Prien
Stade
550 employees
total budget >40 Mio. €
© Fraunhofer IFAM
Presentation overview
Basics Metal foams, definition and structure Manufacturing Properties
Looking back: Review of expectations and realized productions
Looking forward: New developments
Conclusions
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Basics - Definitions
What are „metal foams“ ?
metal matrix
porosity > 50 %
cell structure
solid state
open/closed porosity
Metal Foam
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(Metal) foam structures in general can have:
structural application functional application both
Other characteristics pore size pore morphology matrix alloy
Basics - Definitions
closed porosity open porosity mixed porosity
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Metal foams are not “new” : Al-foam: first trials in 1920's main development in last 20 years several commercialized foams e.g. Alporas, Foaminal, INCO,...
Basics - Production
Foaminal AFS
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cellular and porous metals
metal vapour
PVD
CVD
metallic melt
foaming
spraying
extraction
casting around space holders
investment casting
metal ions
galvanic deposition
metal powder
PM infiltration of space holders
slurry coating
printing
foaming of slurry
powder/binder-processing
reaction sintering
self forming
use of template
Basics - Production
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Basics - Production
Powder metallurgy - Foaminal
Aluminium Zinc Lead
Complex geometries Filled profiles
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Basics - Production
Powder metallurgy: Aluminium foam sandwich (AFS)
foamingfurnace
foamingfurnace
foamable material
rolling mill
conventional material
sandwich structure
conventional materialadhesive
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Deposition techniques space holder: PE-foam metal: Cu, Ni Electroplating/CVD producers: INCO, Retimet, Celmet,…
add
conductive
coating
electroplatepolymer
foam
polymer coating metal
remove
polymer
Basics - Production
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Basics - Properties
Polymeric foams known to be good crash energy absorbers high specific stiffness heat insulation sound and vibration dampening
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Basics - Properties
Common deformation behaviour for all foam structures Stress plateau in compression Metal foams: higher thermal stability, conductivity, strength
33%
[Karmann]
53% 77%
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Basics - Properties
Stiffness: reduced Young’s modulus (but higher specific stiffness!)
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Basics - Properties
Stiffness: reduced Young’s modulus but higher specific stiffness
Compression strength of AlSi12 foams at 20% strain
slope 1.75
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Basics - Properties
Vibration damping
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Basics - Properties
Sound damping sound pressure level of Al foam is below that of CFK for all rpm values reduction of the sound pressure level up to 8 dB
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Looking back
When nature does the same, she generally uses cellular materials:
wood, bone, coral.
„When modern man builds large load- bearing structures, he uses dense solids:
steel, concrete, glass.
Prof. M.F. Ashby, Univers ity of Cambridge
There must be good reasons for it.“
For structural applications:
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Looking back
Examples of implemented applications of open porous foams Energy storage Nickel foams in pasted -electrode batteries (>3Mio. m2 per year) Filter, heat exchanger oil-air separators in aircraft breather plugs heat exchangers in electron microscops (ERG) Crash energy absorber space craft separation shock, shock absorbers for medium tactical vehicles
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Looking back
Examples of implemented applications of closed cell foams Crash energy absorption REUM/Audi Q7, Sprinter light train Combino tram front High specific stiffness, local stiffening and strengthening Mobile telescope platform, Ferrari door sill battery support E3-electric vehicle supports for excavator deck
Damping Textile machine arms support plates for linear axis
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Looking back
Examples of implemented applications of closed cell foams Architecture, design congress center in Mallorca house facade in Bochum Memorial of Service Employees International Union wall cladding of ice rink Other zinc selector-lever
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Looking back - market assessment
Open cell foams: few, very specific mass products
Closed cell foams: mass production for design and architecture other markets: less volume than expected
reduced strength (metal components “strength-designed”) reduced ductility costs
structural foam mostly encased (polymer, casting, sandwich) structures (sandwich) can be welded
© Fraunhofer IFAM
Looking forward
Activities on porous metals started at IFAM at the end of 1980’s
Metal foams
FoaminalTM
aluminium foam
Aluminium foam sandwich
AFS
Aluminium foam granules
APM
Composite (syntactic)
foams
Open porous foams
we started with those...
© Fraunhofer IFAM
Looking forward
Activities on porous metals started at IFAM at the end of 1980’s
Metal foams
FoaminalTM
aluminium foam
Aluminium foam sandwich
AFS
Aluminium foam granules
APM
Composite (syntactic)
foams
Open porous foams
We extended our activities with those...
© Fraunhofer IFAM
Aluminium foam granules
based on Foaminal aluminium foam technology 1mm-15mm, round, elongated as-foamed, surface treated, pre-coated integration into: EPP, EPS, epoxy foams, silicone foams, fibre structures,
nonwoven-textiles polymer-aluminium composite foams
Epoxy Non-woven EPS/EPP
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Aluminium foam granules
easy and - if necessary local - application improved strength reduced fire loads less shrinkage, less curing heat
Advantageous to use for:
Crash energy absorption
Specific stiffness (sandwich)
Local strengthening, vibration damping
Reduced curing heat
EU-Smartbatt
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Composite (syntactic) foams
porosity created by integration of hollow spheres into matrix
well-established for polymers and inorganic non-metal materials, e.g. paint fillers submarine and deep sea technology light-weight concrete
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Composite (syntactic) foams
production using melt infiltration and powder-metallurgical methods
simple and complex shapes aluminium, zinc, steel, stainless steel,...
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Composite (syntactic) foams
mass production techniques (like MIM) available (small process adaptions) easy production of complex near-net-shape products advantageous to use for:
absorption of high crash energy loads damping in harsh environments 2C-components (porous/non-porous)
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Conclusion
metal foams have been established in industrial production still limited number of applications and high-volume products main reasons (for structural foams):
cost strength
focusing on the advantages for successful application!
weldability (esp. of sandwiches) vibration absorption and decoupling crash energy absorption
© Fraunhofer IFAM
Outlook
Current activities: research and development is going on number of applications is slowly growing
Market expectations:
increasing use of metal foam sandwiches (stiff, weldable) increasing use of porous aluminium for heat exchangers and energy
storage
new product types in development o aluminium foam granules o high-strength (syntactic) foams
new market areas will develop
o medicine (stiffness adapted implants)