Lehigh University
Lehigh University


Developing composites for lighter, stronger ships

Engineers from Lehigh and Northrop Grumman Ship Systems have successfully tested ship panels made of lightweight composite materials that have future military and commercial applications.

Joachim Grenestedt

Composite materials – highly engineered glass- or carbon-fiber-reinforced polymers – are lighter and stronger than steel, and more resistant to corrosion.

The project was overseen by Joachim Grenestedt, professor of mechanical engineering and mechanics at Lehigh, who developed a 30-foot-tall drop-weight tower, an “impact bunker” to catch the projectile after impact, and a special “bend test fixture” to measure the effects of the impacts on the composite panels.

Grenestedt and his staff built the drop tower and the impact bunker at Lehigh’s ATLSS (Advanced Technology for Large Structural Systems) Research Center. He dropped a 150-pound projectile on the test panels from various heights to simulate a collision between a fast-moving ship and a heavy floating object.

The results of Grenestedt’s tests, said Dave Whiddon, vice president of research and development at Northrop Grumman, “have already helped reduce risk in one of our composite programs, and will serve to reduce and mitigate risks associated with the future development of composite naval vessels.”

Grenestedt played a major role in the structural design and materials testing of the Visby, a Swedish stealth ship sea-launched in 2000, which, at 239 feet, is the largest carbon-fiber ship ever built.

In 2004, under a contract with the Office of Naval Research, Grenestedt and ATLSS director Richard Sause designed, built and tested a 20-foot model of a new hybrid ship hull consisting of a steel frame and composite sandwich panels. A new contract has just been awarded to fatigue-test a considerably larger hybrid ship hull specimen.

“The entire faculty of the department of mechanical engineering and mechanics could easily stand inside this specimen,” Grenestedt says with a laugh.

Grenestedt, who founded and directs Lehigh’s Composites Laboratory, is deeply involved in composites in his free time. He owns and flies a fast two-seat composite-material airplane, he has designed and built a 23-foot carbon-fiber beam for the deck of his house, and he is building a composite-material “Streamliner” for Land Speed Racing.

Posted on Thursday, August 31, 2006

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