Metal Foams: A Design Guide

F/2 F/2
F/2 F/2
τ Core
Characterization methods 35
Figure 3.8 The sandwich-beam test, configured so that the core is loaded
predominantly in shear
which may be difficult to obtain in practice. The sandwich panel test has the
virtue that it is closely related to the practical application of foams as the core
of a sandwich panel.
3.8 Creep testing
Creep tests are performed using a standard testing frame which applies a
dead load via a lever arm to a specimen within a furnace. The temperature
of the furnace should be controled to within 1°C. Displacement is measured
using an LVDT attached to the creep frame in such a way that although it
measures the relative displacement of the specimen ends, it remains outside the
furnace. Compression tests are performed by loading the specimen between
two alumina platens. Tension tests are performed by bonding the specimens
to stainless steel grip pieces with an aluminum oxide-based cement (e.g.
Sauereisen, Pittsburg, PA). The steel pieces have holes drilled through them
and the cement is forced into the holes for improved anchorage.
Data for creep of aluminum foams can be found in Chapter 9.
3.9 Indentation and hardness testing
Reproducible hardness data require that the indenter (a sphere or a flatended
cylinder) have a diameter, D, that is large compared with the cell size,
d⊲D/d > 7⊳. Edge effects are avoided if the foam plate is at least two indenter
diameters in thickness and if the indentations are at least one indenter diameter
away from the edges of the plate. Because they are compressible, the indentation
strength of a foam is only slightly larger than its uniaxial compressive
strength. By contrast, a fully dense solid, in which volume is conserved during