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12/09/91

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Springer: composite structures - some like baking bread, others like ice sculptures

In the 1960s, engineer George Springer applied with a thousand other hopefuls to NASA's scientist-as-astronaut program.

Springer, who narrowly escaped from Hungary in 1956 at the height of the Communist revolution, longed to see the newspaper headline: "First Man on Moon a Hungarian." At the time, though, NASA was looking for medical doctors to study space's effects on the body and geologists to examine moon rocks. A materials scientist, Springer did not make NASA's final cut.

Nonetheless, without ever stepping onto a launch pad, Springer has made it possible for others to take that giant leap for mankind.

Springer, chair of Stanford's department of aeronautics and astronautics, is a world-renowned materials scientist whose "plastic surgery" has changed the face of vehicle and sports- equipment markets. He works with composite materials, fusing plastics or resins with fibers such as graphite. The parallel orientation of the fiber sheets gives composites ant-like strength for their light weight, low density and moldability.

"These are the materials of the future," Springer said.

As a consultant to industry and government, he has worked on the composites used to create the fiberglass bodies of Pontiac Fieros, windmill blades at Altamont Pass, Beech's Starship I airplane and an artificial heart. The materials have been used to mold objects as diverse as graphite tennis rackets and parts of the space shuttle.

Now, he has brought together the talents of robotics engineers and materials scientists to automate an exotic technique for sculpting composites. The technique provides instant feedback about the shape and strength of hybrid materials as they make their metamorphoses from raw graphite and plastic into finished products.

'Wrong place, wrong time'

Springer was a 23-year-old collegiate ice hockey player in Hungary in 1956 when the Soviet army occupied the country. By chance, he was seized by the Russians and shoved up against a wall to be shot.

"I was in the wrong place at the wrong time," said Springer, who escaped his captors when people in surrounding buildings began shooting at the Russians.

He left the country for Austria and immigrated to Australia to live with an uncle. In 1960, he came to the United States to study fluid mechanics at Yale. There he met his future wife, Susan, daughter of Stanford's Nobel Prize-winning chemist Paul Flory.

After earning his doctorate in 1962, Springer was offered an assistant professorship in mechanical engineering at MIT. Five years later, with a wife and a baby on the way, Springer was lured to the University of Michigan with a promotion and substantial pay raise.

The Springers' daughter was born prematurely.

"There weren't very good respirators in 1967," said Springer, who was inspired to work with doctors to develop a fluidic-controlled respirator - patented in 1970- to accommodate the shallow, panting breath of premature infants.

Did the baby survive?

"The 'baby' is happily married," Springer replied.

While in Michigan, Springer became interested in air pollution caused by cars. He studied the photochemical reactions that result when smog interacts with sunlight. As a technical consultant for the United Auto Workers, his testimony before a House committee helped set the nation's automobile emissions standards.

"I even testified in front of (John) Dingell," he said in reference to the Michigan Democrat who has held House subcommittee hearings on indirect costs. "Being from Michigan, I was on Dingell's good side."

Later the Air Force asked Springer to find a way to reduce the damage caused to aircraft by driving rain. Rain stresses metals "like water torture," he said.

Evaluating various wing coatings, Springer concluded that rubber coatings called elastomers best distributed the energy imparted to the wings by rain.

He developed a method used worldwide to test the resistance of materials to water damage. Called W8GAIN, the test involves boiling the materials for one to three days, measuring their weight gain, examining them for microscopic cracks and rating their strength.

Now, from their basement Structures and Composites Laboratory at Stanford, Springer and graduate students Hugo Sarrazin and Rick Hosey, in conjunction with a team of robotics scientists, are trying to change the way America manufactures goods. They have developed a novel automated technique to manufacture composite materials that could bring cheaper, lighter, stronger and more attractive goods to consumers.

The project's major sponsors are McDonnell-Douglas and the Stanford Integrated Manufacturing Association, an industry- sponsored consortium whose members include Boeing, Lockheed, Ford, General Motors, Alcoa and General Electric.

Ice sculpture, baking bread

Composite structures can be manufactured two ways, Springer said. He likened one method to baking bread, the other to creating ice sculptures.

Currently, manufacturers use the "bread-baking" method, which requires "cooking" resinous epoxy and graphite fibers under high temperature and pressure for hours, days or even weeks. The combination of heat and pressure causes the materials to harden like the crust on a loaf of bread, he said. Compounds that use resins to bind together the fibers are called thermosetting composites.

Cooking the materials under pressure requires an oven big enough to accommodate objects as large as parts of airplane wings. The process is tricky: one can "overcook" or "undercook" the materials, ruining the formation of the matrix - pattern of fibers in the resin.

As a way to gain better control over the manufacturing process, Springer favors the "ice sculpture" method, used to produce thermoplastic composites, those in which plastic instead of epoxy binds the fibers. Materials are heated to 800 degrees Fahrenheit, then molded around forms and cooled to room temperature, where they set into their permanent shapes.

Springer demonstrated the prototype for thermoplastic manufacturing in his laboratory: A robot lays successive plies of plastic tape over a form. To bond the layers together, the robot blows hot nitrogen gas over the tape while its roller-arm applies 50 to 100 pounds of pressure.

Sensors embedded in the tape layers relay the material's status to a computer, which immediately tells the robot to adjust the temperature, pressure or tapelaying speed. Several robot arms could work on the same structure at once, speeding up production, Springer said.

The U.S. Air Force first used prototype expert systems fast enough to control the manufacturing process as it occurs. "But Stanford's system is much more sophisticated," Springer said.

Composite materials are not as cheap as plastics and do not operate at high temperatures as well as ceramics. However, because they combine the beneficial properties of metals, plastics, fibers, resins and ceramics, they have been used to manufacture goods as diverse as portable iron lungs and submarines, said Springer.

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