The Tech Report reports Apple seems to be experimenting with carbon fiber designs:
Even the most ardent Apple critics have to admit that the aluminum unibody enclosures that encase MacBook Pro laptops are all kinds of sexy. Industrial design has long been a strong suit of the Mac maker, and it looks like the future could hold less metal and more woven carbon. Kevin Kenney, former president of carbon fiber bicycle specialist Kestrel, is now a "senior composites engineer at Apple," according to his LinkedIn profile.
Engadget notes that Kenney has worked with Apple before. Back in 2010, Kenney and Apple filed for a patent on carbon-reinforced housings for electronics devices.