Tough material gets functional

A University of California at San Diego researcher has made several useful versions of a metallic material that is as stiff as steel but only half as dense.

The material was inspired by the red abalone, a California mollusk that constructs its mother-of-pearl shell from alternating microscopic layers of calcium carbonate and a protein adhesive. The researcher made the metallic material from layers of titanium aluminide that mimic the shell's hard calcium layers, and titanium alloy that mimics the tough protein.

The new versions of the material could eventually be used as building materials, bullet-stopping armor, and a replacement for the strong but toxic metal beryllium in aerospace applications.

The researcher built the material by pressing together titanium aluminide and titanium foil layers under high pressure and high temperature. He made the new functionalized versions that contain embedded objects by forming cavities in the layers before pressing them, then filling the cavities with steel beads, tubes, wires or optical fibers.

The steel-bead-filled version of the material is designed to dampen vibrations and is appropriate for applications prone to noisy vibration like jet engines. The tubes in embedded in the second version of the material can collapse to absorb blast energy, carry fluids to exchange heat, or be used to carry out chemical reactions. The versions with embedded electrical wires or optical fiber can be used to detect damage in the material or connect embedded sensors and micromechanical devices.

The researcher also made a device from the material that contained embedded electrical wires connecting cavities filled with piezoelectric crystal; signals from the piezoelectric crystal sensors can be used to determine the locations and magnitudes of impacts on the material.

The fabrication method can also be used to build other types of layered metallic materials, according to the researcher.

The work appeared in the March 8, 2005 issue of The Journal of the Minerals, Metals and Materials Society.