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