Characteristics of closed cell aluminum foams

Characteristics of Closed Cell
Aluminum Foams
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Efficient energy absorption
Excellent stiffness-to-weight ratio
Nearly isotropic - Multiaxial loading
Low thermal conductivity
Fire resistant
Shock wave attenuation
Sound and vibration damping and absorption
Tailorable density and properties
Recyclable


Production Process for
Aluminum Foam Parts
Mixing

Press

Extrusion
press

F

Al - Powder
(Alloys)
+TiH2 - Powder
CIP

Foamable
precursor

Mold

Heating

Foaming
T ~ 700 °C

Aluminum foam
3-D-part


Al Foams: Flat plates and 3-D shapes for
cores in lightweight aluminum castings


Quasi-Static Behavior of Aluminum Foam
60
ρ0
ρ0
ρ0

ρ0

Engineering Stress, MPa.

50

=
=
=
=

0 .8 2
0 .5 7
0 .4 7
0 .3 4

gm
gm
gm
gm

/c c
/c c
/c c
/c c

40

30

20

10

0

0

0 .1

0 .2

0 .3

0 .4

E n g in e e r in g S t r a in .

0 .5

0 .6

0 .7


Aluminum Foam Filled 304SS Tubes
After Axial Compression


3-D molded foam shape for auto

crash energy absorption


Aluminum foam insert used for stiffening
and energy absorption in auto side rail


Tailorability of Aluminum Foams
50

10
σ [MPa]

1
0.5
3
Density (g/cm )

1.0

Plateau stress of Al-12Si foams as a function of foam density


Tailorability of Aluminum Foams
E [GPa]
50

10

1

0.5

0.1

1.0

Relative density

Elastic modulus of Al-12Si foams as a function of density


Aluminum Foam Used in Hybrid Vehicle Armor

Alumina Ceramic
Aluminum Foam
Fiber reinforced polymer

Cross-section through lightweight armor using aluminum
foam layer, after 20 mm FSP ballistic testing for the U.S. Army.
Aluminum foam impedance layer provides:
• Improved defeat of projectile
• Enhanced ballistic shock wave attenuation
• Lower dynamic deflection of backplate


Aluminum Foam Frame for Ballistic
Stress Wave Management

External Aluminum Foam
Frame Offset Impact

Force measurements for shots 13-16
Without Al Foam vs. With Al Foam

Location 2

Location 3

0

0

-5
-5

3
Force(Kilo-Lb)

Force(Kilo-Lb)

-10

-15

-20

-25

-10

-15

2

-20
No Al foam
No Al foam
With Al foam
With Al foam

-30

-35
0

0.2

0.4

0.6
0.8
Time (ms)

1

1.2

No AL foam

No AL foam
With AL foam
With AL foam

-25

-30

0

0.2

0.4

0.6
0.8
Time (ms)

1

1.2


External Aluminum Foam
Frame - Center Impact

Acceleration Measurements
Without Al Foam vs. With Al Foam

3TEX-4A- 2 W ithout AL foa m

12

12

10

10

Shot 2

6
4
2
0

6
4
2
0

-2

-2

-4

-4

-6

-6

-8

0

2

4
6
Time (ms )

Shot 3

8
Acceleration(Kilo-g)

8
Acceleration(Kilo-g)

3 TEX -4A -3 W ith AL f oam

8

-8

0

2

4
6
Time (ms )

8


Vibration Damping Tests on Al Foam
and Bulk Al Sheets

3 mm
Al sheet
5 mm
Al sheet
25 mm
Al foam

Weight
(kg)

Area
(mm)

1.9

500x500

3.3

500x500

2.0

500x500


Test apparatus for vibration
damping measurements
Impact hammer
with force
sensor

Acceleration sensor

Tested
panel


Frequency Response Curves
After Impact by Hammer
3 mm Al-sheet; Weight:1,9 kg

5 mm Al-Sheet; Weight: 3,3 kg

25 mm Al-Foam panel; Weight: 2 kg

Inertance a/F (ms-2/N)

1600

1400

-2

1200

1000

800

600

400

200

0
0

500

1000

1500

2000

Frequency (Hz)

2500

3000

3500


Damping of vibration after impact by hammer
as measured by surface accelerometer
Acceleration a [ms-2]

300

3 mm Al-sheet; Weight:1,9 kg

200
100
0
-100

0

50

100

150

200

250

200

250

-200
-300
-400
Time (ms)

Acceleration a [ms-2]

300

5 mm Al-Sheet; Weight: 3,3 kg

200
100
0
-100

0

50

100

150

-200

-300
Time (ms)

150
Acceleration a (ms-2)

25 mm Al-Foam panel; Weight: 2 kg

100
50
0
-50

0

50

100

150

-100
-150
Time (ms)

200

250

Damping factor (decay) of 25 mm Al foam
panel vs. 3 mm and 5 mm Al sheets
3 mm Al-sheet; Weight:1,9 kg

5 mm Al-Sheet; Weight: 3,3 kg

25 mm Al-Foam panel; Weight: 2 kg

Decay - Damping factor Eta (-)

1,4E-02

1,2E-02

1,0E-02

8,0E-03

6,0E-03

4,0E-03

2,0E-03

0,0E-03

0

500

1000

1500

Frequency (Hz)

2000

2500


Aluminum Foam Blast Testing


Blast Loading of Aluminum Foam Panels
Test Configuration
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Front plate
Al Foam panel
Back plate

(18 in. x 18 in. test area)
1/8 inch thick steel
2 inch thick Al-7Si – 20% density
1/4 inch thick steel

Loading Conditions

Explosive: 1 kg PETN

Standoff distance

Blast Test Results

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2 meter

No noticeable damage to foam or steel

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0.5 meter

50% deformation of foam
No back plate deflection

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0.1 meter

60-80% deformation and fracture of foam
Steel plates deformed but not perforated


Blast test panels after exposure to detonation
of 1 kg PETN at 0.1 m standoff distance

Left:
Center:
Right:

Front steel sheet – 1/8 in. thick
Aluminum foam
Back steel plate - 1/4 in. thick


Compressive plastic deformation and fracture
of aluminum foam exposed to 1 kg PETN explosive
at 0.1 m standoff

Aluminum experienced up to 70-80%
compressive strain in local regions under
1/8 in. thick steel front cover sheet


Aluminum Foam Sandwich Panels
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Low-density Al alloy closed cell foam cores

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Al foam cores metallurgically bonded to Al
alloy face sheets

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Sandwich geometry provides very high
stiffness-to-weight and strength-to-weight
ratios

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Available in panel sizes up to 48 x 96 x 0.35
to 4 inch thick


Aluminum Foam Sandwich
panels in various thicknesses


Unfoamed AFS precursor sheets
3100 x 1100 x 2.5 mm