A growing trend in the manufacture of composite structures is the use of extruded shapes fabricated with tools made of Invar 36, a special nickel alloy, says Plymouth Tube, which is now producing such extrusions at its plant in Hopkinsville, Kentucky. Although Invar 36 is not a new material, its tooling use is growing behind increased use of advanced composites by aircraft and missile makers, said Plymouth marketing manager Dennis Gudgel.

Invar's unique combination of durability and low coefficient of expansion minimize thermal expansion mismatch between disparate materials during the curing process and, more importantly, the warping that can follow, Gudgel said. And the low CTE makes Invar attractive not only for tooling but for primary structures and space and cryogenic applications where extremes of temperature vary widely.

Composite extrusions and examples of cold-drawn, seamless hard aluminum tubing are being shown by Plymouth in the U.S. pavilion.