Stealth Bomber Skin Makes Strong Bridges
SOME day, Californians may no longer have to worry about massive concrete bridges crumbling underneath their cars or crushing them during earthquakes.
The proof lies below three normal-looking highway ramps, just north of Dodger Stadium in Los Angeles. Two years ago, the ramps were upgraded to survive quakes - not with concrete or steel, but with the same lightweight, once-secret fibers used to make the stealth bomber.
And when the earth shook hard Jan. 17, the ramps held.
``What we have are the beginnings of an entirely new type of material for the civil construction industry,'' says Frieder Seible, a University of California structural engineer.
A San Diego company, Hexcel Fyfe, weaves fibers of glass and Kevlar (the material in bulletproof vests) into a flexible material that feels like cloth. The material is wrapped around bridge supports, then soaked in an epoxy resin, essentially a strong glue, which turns it into a hard shell. The day after the Los Angeles quake, company owner and chemical engineer Edward Fyfe inspected the experimental composite-wrapped columns just north of downtown Los Angeles, 20 miles from the quake's epicenter. ``We took pictures,'' he says. ``There was no damage.''
Mr. Seible, his colleagues, and a consortium of private companies, including Hexcel Fyfe, are working to prove composites' safety. Last year, they won a $10 million federal defense-conversion grant to build the world's first bridge made entirely of composites. Construction on the 450-foot-long span over Interstate 5 in San Diego will start in three years.
But some skeptics say Seible's defense-conversion dream is still years off. They say composite materials must prove they are durable and cost-effective before governments can routinely use them to build bridges.