Foams are gas filled integral structures in which the gas is finely
dispersed throughout acontinuouslyconnected solid phase. The bulk
density is usually substantially lower than that of the solid component,
and for the foams which form the focus for this book the volume fraction
of the gas phase is considerably greater than 0.5 and in most instances
in excess of 0.9. Many ofthe materials encountered in every day
experience, such as bread, plants and trees, structural materials for
buildings, comfort materials for domestic and automotive seating, shock
absorbers or car bumpers and materials for noise control, have one thing
in common - the cellular nature of their physical structure. Whyare
thesestructuressoimportantin the naturaland man-made world? The reasons
are both technical and commercial. From a technical viewpoint cellular
materials offer: 1. high specific stiffness and strength - making them
suitable for structural applications; 2. closeto idealenergymanagement -
hencetheir useinthermalandacoustic insulation, vibration damping,
acoustic absorption and shock mitigation; and 3. comfort - hence their
use for domestic and automotive seating.