THE WEIRD properties of a mysterious foam have been measured for the first
time. The US Air Force researchers who did the job say the foam could replace
several different types of material, including glass fibre and aluminium
honeycomb, in planes and spacecraft.
Called graphitic foam, it was first made at the US Air Force Research
Laboratory at the Wright-Patterson Air Force Base in Ohio. They melted a liquid
crystal polymer under pressure in an inert gas atmosphere, forcing the gas to
dissolve in the melt. When the pressure was released, bubbles of gas formed
inside the material, creating foam. Heating this in an oxygen atmosphere formed
graphite crystals, which are extremely strong.
Researchers first tried to measure the foam鈥檚 mechanical properties by gluing
strain gauges to it, but glue seeped into the foam and changed its composition.
Now the researchers at AFRL have built precision equipment to carry out
extensive tests, which showed that the foam has three times the stiffness of
aluminium honeycomb. And unlike fibre-based composites and honeycombs, which are
strong in only two dimensions, the graphitic foam retains its properties in
three dimensions.
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These properties mean it can perform several functions at once. For example,
in a space shuttle it could carry heat and electrical charge from one
part of the structure to another, and provide mechanical strength.