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Introduction to Foams

Solid foams

What is a solid foam?

Solid foams are cellular materials, i.e. materials which are made up from a framework of solid material surrounding gas-filled voids (bubbles). Solid foams can be 100 times lighter than the equivalent solid material.

Natural solid foams include wood, bone and sea sponges. The bee's honeycomb is a two-dimensional cellular structure:

A honeycomb

Recent developments in metal foams, especially aluminium, have produced a new class of lightweight materials, which are excellent energy absorbers. This property is useful in reducing the impact of a car crash.

Other applications of solid foams include:

• Cushioning materials in furniture.
• Structural materials such as sandwich board.
• Insulating materials, such as cavity wall insulation.
• Packaging materials, such as expanded polystyrene.
• Several food items, such as bread, cake and other snack foods.