| Many
materials have a cellular
structure, with either a two-dimensional array of prismatic cells, as
in a honeycomb, or a three-dimensional array of polyhedral cells, as in
a foam. Engineering honeycombs and foams can now be made from
nearly
any material: polymers, metals, ceramics, glasses and
composites, with
pore sizes ranging from nanometers to millimeters. Their
cellular
structure gives rise to a unique combination of properties which are
exploited in engineering design: their low weight make them attractive
for structural sandwich panels, their ability to undergo large
deformations at relatively low stresses make them ideal for absorbing
the energy of impacts, their low thermal conductivity make them
excellent insulators, and their high specific surface area make them
attractive for substrates for catalysts for chemical
reactions.
Cellular materials are increasingly used in biomedical
applications.
Open-cell titantium foams are used to replace trabecular
bone. Porous
scaffolds for regeneration
of damaged or diseased tissues often
resemble an open-cell foam. Cellular materials are also
widespread in
nature in plant and animal tissues: examples include wood,
cork, plant
parenchyma, trabecular bone and lung alveoli. |
A two-dimensional random Voronoi honeycomb.
(From
Gibson and Ashby, 1997)