A quarterly research and development magazine
Technical contact
Dennis Roach
(505) 844-6078
dproach@sandia.gov
Media contact
John German
(505) 844-5199
jdgerma@sandia.gov
Underneath a New Mexico highway overpass, on either side of an I-beam that supports the bridge, are two composite-fiber patches, each about the size of a car’s license plate, installed by Sandia engineers.
The patches represent a successful repair job on a small crack that had formed in the steel beam. Sandia installed the repair on the bridge earlier this year.
The demonstration is an outgrowth of Sandia’s decades of work, sponsored by the Federal Aviation Administration, to develop and evaluate technologies that extend the service lives of aging aircraft. The repair demonstration was funded by the program.
The stronger-than-steel composite repair technique is performing well, says Sandia project lead Dennis Roach, whose team is monitoring the repair over time using embedded sensors that watch for signs that the crack is growing.
The patches — a fast, inexpensive alternative to steel plates or more extensive repairs — are made of flexible, fiber-reinforced composite material adhered to the steel’s surface. Produced as a thin tape, the material comprises strong, parallel boron fibers enmeshed in epoxy.
Layers of the tape are successively applied with an adhesive, forming a multilayer laminate. The finished repair is a fraction of an inch thick and much stronger than a typical riveted steel patch of comparable thickness.
Composite doublers are corrosion resistant and lightweight and can be readily formed into complex shapes without machining.
Bonding composite patches to a metal structure, rather than bolting on a traditional steel patch, also eliminates the need to drill fastener holes that decrease the structure’s strength and can act as new crack-initiation sites, says Roach.
Composite patches have gained acceptance in the commercial aviation sector as strong, flexible, lightweight repairs for commercial aircraft. More recently, the Sandia team has been evaluating and testing similar techniques for a variety of other safety-critical structures.
“This project took a technology developed for aircraft repair and applied it to massive steel structures where safety is of utmost concern,” says Roach. “While lower-strength fiberglass has been used to repair concrete, this is the first application on a steel superstructure.”
©2010 Sandia Corporation | Questions and Comments | Privacy and Security | 
News release RSS feed