Metal Foams: A Design Guide

Properties of metal foams 49
show the indices E/ , E 1/2 / and E 1/3 / . Their significance is discussed
in Chapter 5. Metal foams have attractively high values of the last of these
indices, suggesting their use as light, stiff panels, and as a way of increasing
natural vibration frequencies.
Strength and density
Ł Figure 4.7 shows compressive strength, c, plotted against density, for
currently available metal foams. For clarity, only some of the data have been
identified. The numbers in parentheses are the foam density in Mg/m 3 .The
2/3
1/2
broken lines show the indices c/ , c / and c / . Their significance is
discussed in Chapter 5. Metal foams have attractively high values of the last
of these indices, suggesting their use as light, strong panels.
Compressive strength (MPa)
100
Compressive strength
vs Density
Fraunhofer (0.7)
Fraunhofer (1.1)
Fraunhofer (0.8)
Manual1.CMS; MFA 21-11-97; Metfoam DB Hydro (0.56)
Alulight (1)
Hydro (0.5)
Alulight (0.751)
10
Hydro (0.34) Alulight (0.5)
Duocel (0.235)
Cymat (0.541)
Alulight (0.65)
Alulight (0.95)
Alporas (0.21)
Duocel (0.19)
Alulight (0.7)
Hydro (0.15)
Alulight (0.55)
1
sc Duocel (0.162)
r
Hydro (0.156)
Hydro (0.449)
Alporas (0.245)
s 2/3
c
r Hydro (0.143)
Cymat (0.276)
Hydro (0.194)
INCO (0.385)
0.1
s 1/2
c
r
Cymat (0.166)
0.1 0.2 0.4
Density (Mg/m
0.6 0.8 1
3)
Figure 4.7 The compressive strength plotted against density for currently
available metal foams. Output from CES3.1 with the MetFoam ’97 database
Specific stiffness and strength
Stiffness and strength at low weight are sought in many applications. Caution
must be exercised here. If axial stiffness and strength are what is wanted, the
proper measure of the first is E/ and of the second is c/ . But if bending
stiffness and strength are sought then E 1/2 / and 2/3
c / (beams) or E1/3 /
and 1/2
c
/ (panels) are the proper measures.