Aluminium encyclopaedia

Composite materials

Preformed materials made from aluminium with plastics, other metals or textiles are used for many applications. As the joint cannot be separated mechanically, these products are called "composite materials". With metals, the joint is made by electroplating (see coating), soldering or brazing, or roll bonding (rolling together at elevated temperatures); with plastics and textiles it is produced by adhesive bonding or vacuum deposition. The aim is to increase corrosion resistance or strength, as well as saving weight while maintaining the same strength.

A selection of composites and manufacturing processes:

  • Cladding of aluminium alloys with unalloyed aluminium increases the corrosion resistance, for example of Duralumin in aircraft construction (first used in 1926 in the USA).
  • Aluminium cores clad on one or both sides with steel serve as adapters for joints between aluminium and steel (aluminium is then joined to aluminium and steel to steel) or as heat-distributing bases in cookware (see household equipment).
  • Aluminium plated with lead provides shielding for radiation in radiation medicine and nuclear technology (lead absorbs ionising rays very effectively, aluminium gives the shielding strength and low weight).
  • Aluminium rods are roll-bonded with copper and then processed by drawing to wire for household wiring or to battery cable for road vehicles. The copper overlay makes it possible to use joining technologies normally used for copper, such as soldering or brazing, between these aluminium wires and all-copper wires.
  • Lamination of aluminium foil with plastic film and/or paper produces composite packaging materials.
  • Textiles, vapour deposited with aluminium or laminated with aluminium foil, are used as heat protective clothing for blast-furnace workers and firemen.
  • Sandwich panels, three to eight millimetres thick, consist of two anodised or coated surface layers made of corrosion resistant aluminium alloys and a plastic core, and are used as façade cladding in building construction. They are stiff and can be easily installed using screws, riveting or adhesive bonding.
  • Similar, but thicker plate with a thermally insulating core made of plastic, mineral wool, aluminium foam or foam glass is used for self-supporting cladding panels, as well as for curtain-walls, door infill panels and roofing.
  • Components having a core of aluminium honeycomb, balsa wood or foamed aluminium between two outer layers of high-strength aluminium alloy are widely used in aircraft construction and space travel; they are lightweight but stiff.

Lightweight containers made from extruded aluminium tube with a fibre-reinforced plastic sheath are used to store and transport gases.