HIGH-TECH TOOLS TEST COMPOSITE STRUCTURES

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LA JOLLA, CALIF. — Improved methods are emerging to monitor the soundness of structures made with advanced composite materials, according to speakers at the Wilson Forum, held April 7-8 in La Jolla.

Use of so-called smart technologies requires ``a truly multidiscipline approach,'' said Roger Davidson, manager of materials technology for AEA Industrial Technology in Didcot, England.

``Continued development and miniaturization of sensors and the introduction of lightweight, high-performance computers will accelerate the uptake of smart ideas into smart products,'' Davidson said.

A. Emin Aktan, professor of infrastructure studies at the University of Cincinnati, emphasized the need in any program for ``sufficiently trained'' structural, geotechnical and electrical engineers and an industry recognition of ``the significant potential of this emerging tool.''

Jeffrey Gentry, vice president of software development for Digital Wave Corp. in Englewood, Colo., described use of modal acoustic emissions and ultrasonics in the nondestructive evaluation of composite materials.

He noted that a pulse-wave ultrasonic approach requires access to only a single side of a specimen and can compute a material's stiffness from measured extensional and flexural mode velocities. Embedding a thin, coated optical fiber avoids the need for a conventional sensor's high-conductivity cabling, said Julian Fells, an engineer with the microwave and photonics division of GEC-Marconi Materials Technology Ltd. in Towester, England.

``Optical fiber strain sensors are now a practical technology for the structural health monitoring of various structures,'' Fells said.

The firm has succeeded in field tests of a prototype strain-sensing system using the fiber.

Speakers acknowledged that monitoring is feasible in construction of new highway bridges, but difficult to implement in retrofit programs.