Metal Foams: A Design Guide

126 Metal Foams: A Design Guide
Table 10.2 Material properties
Property Face Foamed Solid
core core
Density (kg/m 3 ) f c s
Young’s modulus (GPa) Ef Ec Es
Shear modulus (GPa)
Yieldstrength(MPa)
– Gc –
f c
s
y
y
y
c Yieldstrengthinshear(MPa) – y –
Notation
b D width
c D core thickness
t D face sheet thickness
ℓ D span length
W D weight
P D load
p D load per unit area
1. A specific example is given for the case of a sandwich plate subject to
a uniformly distributed transverse load. This example illustrates issues
and procedures related to designs that limit deflections, subject to strength
criteria. It then demonstrates how optimization is achieved in terms of a
dimensionless load index 5 and weight index .
2. Following this example, generalized results are presented for stiffnesslimited
sandwich beams and plates. These results apply to a range of
loadings and give non-dimensional strengths for the local and global weight
minima at a specified stiffness.
3. Sandwich panel results are compared with results for waffle-stiffened
panels, in order to establish domains of preference.
4. Strength-limited sandwiches are considered and compared with stringerstiffened
construction. Cylindrical sandwich shells are emphasized because
these demonstrate clear weight benefits over conventional designs.
5. Overall recommendations regarding sandwich design are given.
10.6 Illustration for uniformly loaded panel
The design of a wide sandwich plate subject to a uniform distributed load will
be used to illustrate how the thicknesses of the skins and the cellular metal
core are chosen to produce a weight-efficient plate. The structure is shown in
Figure. 10.9. The plate is simply supported along its long edges. The span ℓ
and the load per unit area p are prescribed. The cellular metal core material is
assumed to be pre-selected, such that the analysis can be used to explore the