Stealth Bomber Skin Makes Strong Bridges
SAN DIEGO — 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.