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A look back and forward

Metal foams, the light-weight material of the future?

Dr.-Ing. Jörg Weise Fraunhofer IFAM, Bremen Germany

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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

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Magdeburg

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Fürth

Wachtberg

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Oldenburg

Freiberg

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Gießen Erfurt

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Bayreuth

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Prien

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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. €

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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

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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...

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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...

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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

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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)