Metal Foams: A Design Guide

Stress, σ
Schematic
Young's modulus, E
Energy absorbed
up to densification
Strain, ε
Plateau
stress, σ pl
Densification strain, ε D
Properties of metal foams 45
Figure 4.2 Compression curve for a metal foam – schematic showing
properties
Stress (MPa)
Stress (MPa)
14
12
10
8
6
4
2
0
0
8
6
4
2
a
b
10
20
Longitudinal
Transverse
30
40
Strain (%)
Longitudinal
Transverse
50
60
ρ/ρ s = 0.12
Cymat
Alporas
0
0 20 40 60 80 100
Strain (%)
70
80
ρ/ρ s = 0.11
Figure 4.3 Compression curves for Cymat and Alporas foam
the shear modulus, G, and Poisson’s ratio scale with density as:
�
E ³ ˛2Es
�n G ³ 3
8 ˛2Gs
� �n ³ 0.3 ⊲4.1⊳
s
s
where n has a value between 1.8 and 2.2 and ˛2 between 0.1 and 4 – they
depend on the structure of the metfoam. As a rule of thumb, n ³ 2. For design