The markets: Civil infrastructure (2011)
Despite demonstrable lifecycle-cost advantages, composites continue to meet resistance from civil engineers faced with first-cost restrictions. In 2009, a promising new strategy that combines composites and conventional materials offered an affordable alternative.
More than 250,000 deficient or obsolete structures, such as bridges and parking garages, need repair, retrofit or replacement in the U.S. alone. The U.S. Research and Innovative Technology Admin. says that more than 150,000 of the U.S.’s 600,000 bridges are structurally deficient or obsolete. These numbers have stimulated development of a number of composite enabling technologies. An innovative example is the “bridge in a backpack” concept from the University of Maine’s Advanced Structures and Composites Center (Orono, Maine). It features structural fiber tubes that can be folded to duffel-bag size for transport, then inflated at the work site and infused with resin on a portable frame to form lightweight hollow arches. Anchored side-by-side in footings on opposite sides of the span, the arches are filled with concrete and covered with composite panels that support the roadway. Center director, Dr. Habib Dagher says 50 percent of U.S. bridges now in need of replacement span 70 ft/21m or less, making them good candidates for this technology. Notably, the new technology can compete on a first-cost basis with concrete and steel. Seven such bridges have been installed.
Infrastructure Composites International (San Diego, Calif.) built an advanced composite bridge for the Illinois Department of Transportation and the city of Fairview Heights, Ill. The 38-ft/11.6m long composite vehicular bridge weighs 75 percent less than traditional steel or concrete bridges. For that reason, installation of the bridge took less time, involved less expense and required less labor and heavy equipment than a traditional bridge. The bridge has a projected service life of 50 to 75 years.
In Fort Eustis, Va., Axion International Holdings Inc. (New Providence, N.J.) built two railroad bridges constructed from 100 percent recycled thermoplastic materials. The short-span bridges are based on Axion’s patented Recycled Structural Composite (RSC) system, which consists of nearly 100 percent recycled post-consumer and industrial thermoplastics and is developed in collaboration with researchers at Rutgers University. The bridges reportedly can support 260,000 lb (118 metric tonnes) and are approximately 12.2m/40 ft and 24.4m/80 ft long.
Approaching rollout and first flight, the 787 relies on innovations in composite materials and processes to hit its targets
The structural properties of composite materials are derived primarily from the fiber reinforcement. Fiber types, their manufacture, their uses and the end-market applications in which they find most use are described.
The matrix binds the fiber reinforcement, gives the composite component its shape and determines its surface quality. A composite matrix may be a polymer, ceramic, metal or carbon. Here’s a guide to selection.