University of Delaware
Office of Public Relations
The Messenger
Vol. 6, No. 1/1996
Bridging Cracks in our Infrastructure

     Composites are materials that are made up of two or more
components but have properties superior to those of any one
component alone. A main research focus of the University of
Delaware has been fiber-reinforced composites in which a metal,
polymer or ceramic matrix is reinforced with fibers of graphite
or glass. Composites have higher stiffness-to-weight and strength-
to-weight ratios than conventional materials like metals. In
addition, they resist fatigue and denting, and they don't rust.
     
     Three UD faculty members, along with a number of graduate
and undergraduate engineering students, are building bridges for
the future and saving bridges from the past.
     Michael Chajes and Dennis Mertz, associate professors in
civil and environmental engineering, and Jack Gillespie,
technical director of the Center for Composite Materials and an
associate professor of materials science and civil engineering,
are working closely with industry, government transportation
agencies, private contractors and construction companies to apply
the latest composites technology to an aging infrastructure.
     The team is focusing on using composites to repair old
bridge structures and build new ones.
     The joint initiative, formally called "Applications of
Advanced Materials to Civil Infrastructure," started in the early
1990s. Several projects are in progress as a result of
collaboration among the University, the Delaware Department of
Transportation, the Federal Highway Administration, the Delaware
River and Bay Authority and Hardcore-DuPont.
     According to Chajes, composite materials are being tested in
a campus laboratory and at field sites to determine the
possibility of replacing traditional steel and concrete in bridge
construction and repair.
     While composite materials may seem more expensive initially,
the UD team is working to prove their longer life span. The team
also believes, Chajes says, that use of composites will lower
construction costs because projects can be completed in a shorter
amount of time than those using traditional methods and
materials.
     According to Mertz, explaining the benefits of composite
materials to contractors and their employees is another area the
team must address.
     Even skeptics say they  were  impressed with a study that showed 
how applying composites might have made it possible to avoid the costly 
demolition of a 1940s-era bridge and the construction of a new one in 
Pennsylvania.
     Not only would a repair with composite materials cost less,
it also could have been accomplished more quickly, minimizing
traffic disruptions, Mertz says.
     Gillespie says when composites are applied to bridges that
need repair, the structures' load-carrying capabilities are
increased. In some cases, they support more weight than when they
were originally built. In fact, Gillespie adds, the application
of composites can enhance the capabilities of bridges in good
condition.
     In the scientists' Du Pont Hall laboratory, corroded and
cracked steel beams taken from deteriorating roadways have had
carbon fiber composites bonded to them. Some of the composites
are 1/4-inch thick strips, while others look like sheets of thin
black wallpaper, measuring as little as 5/1000 of an inch in
thickness.
     Chajes says when the paper-thin sheets of carbon fiber
composites were applied with an epoxy to the underside of a
bridge on Foulk Road, north of Wilmington, Del., the longitudinal
cracks that had formed on the beams were arrested. The bridge has
shown no signs of deterioration since it was repaired two years
ago.
     Although this research initiative is in the early stages,
Gillespie says the University team plans three major field
applications in Delaware in collaboration with its partners.
These include a 70-foot-long bridge near the Delaware Memorial
Bridge, a 30-foot-long bridge near Glasgow, on Route 896, and an
overpass over Interstate 295. About 75 percent of the structures
will be made of composite materials.
     "Our efforts," Gillespie says, "will affect the culture of
construction, use of materials and activities in the workforce.
The use of composites, and the potential for their widespread
utilization, will have a dramatic effect on the traditional labor
force. We're trying to put ourselves in their position as we
develop our methods and procedures, so these materials can be
applied by the typical construction worker."
     Because of his background as a bridge designer, Mertz has
devoted a good portion of his time to explaining the project
team's plans to bridge engineers and fabricators and
incorporating their comments and suggestions into the UD
initiative's procedures and planning.
     If the Delaware projects are successful, Chajes says, then
application of this technology will increase nationwide.
     All the components are present for the University to become
a national leader in this area, Gillespie says: Supportive
cooperation with the state, a local industry that can produce
composite materials and excellent research talent at the
University, including a number of civil and environmental
engineering students who are involved with the project.
                            -Ed Okonowicz, Delaware '69, '84M