Metal Foams: A Design Guide

Chapter 1
Introduction
Metal foams are a new, as yet imperfectly characterized, class of materials with
low densities and novel physical, mechanical, thermal, electrical and acoustic
properties. They offer potential for lightweight structures, for energy absorption,
and for thermal management; and some of them, at least, are cheap. The
current understanding of their production, properties and uses in assembled in
this Design Guide. The presentation is deliberately kept as simple as possible.
Section 1.1 expands on the philosophy behind the Guide. Section 1.2 lists
potential applications for metal foams. Section 1.3 gives a short bibliography
of general information sources; further relevant literature is given in the last
section of each chapter.
At this point in time most commercially available metal foams are based on
aluminum or nickel. Methods exist for foaming magnesium, lead, zinc, copper,
bronze, titanium, steel and even gold, available on custom order. Given the
intensity of research and process development, it is anticipated that the range
of available foams will expand quickly over the next five years.
1.1 This Design Guide
Metallic foams (‘metfoams’) are a new class of material, unfamiliar to most
engineers. They are made by a range of novel processing techniques, many still
under development, which are documented in Chapter 2. At present metfoams
are incompletely characterized, and the processes used to make them are
imperfectly controled, resulting in some variability in properties. But even the
present generation of metfoams have property profiles with alluring potential,
and the control of processing is improving rapidly. Metfoams offer significant
performance gains in light, stiff structures, for the efficient absorption of
energy, for thermal management and perhaps for acoustic control and other,
more specialized, applications (Section 1.2). They are recyclable and nontoxic.
They hold particular promise for market penetration in applications in
which several of these features are exploited simultaneously.
But promise, in today’s competitive environment, is not enough. A survey
of the history of development of new material suggests a scenario like that
sketched in Figure 1.1. Once conceived, research on the new material accelerates
rapidly, driven by scientific curiosity and by the often over-optimistic