Acer, Asus Using Fiberglass to Keep Ultrabook Cost Low
Acer plans to release a 15-inch ultrabook with a fiberglass body in early 2012. Asus also plans to use fiberglass in future ultrabook models.
Industry sources report that Acer plans to launch a 15-inch ultrabook in early 2012 built with a fiberglass chassis manufactured by Mitac Precision Technology. Acer was originally scheduled to ship the ultrabook in Q4 2011, but reportedly chose to stall its release due to "unfavorable market conditions."
Asus, Acer and other companies have complained for months about the cost of manufacturing Intel's proposed new form factor while keeping the consumer price tag at the projected sub-$1000 point. The biggest obstacle they face thus far is the price of Intel's processors, but so far the company hasn't offered any kind of subsidy.
According to sources, the price of a fiberglass chassis will be $5 to $10 less expensive than those built using aluminum alloy, and will supposedly knock $20 off the cost of manufacturing the entire ultrabook. Fiberglass will also make the ultrabooks more lightweight than using aluminum. Sources said Acer plans to outsource these fiberglass ultrabooks to Compal Electronics.
In related news, Asus is also expected to use fiberglass cases from the same supplier for future ultrabook models. Currently the company is slated to officially introduce the aluminum-based UX21 and UX31 at a big event next week in New York City. Notebook Italia reports that these will be called "Zenbooks" based on the name provided in the title of the information request form on the ASUS UX countdown site. Since that report, the information request form has been removed.

Cheers!
If only carbon-fiber were cheaper...
Because even aluminum chassis Ultrabooks will bend and break if you sit on them- once the frame's bent the Macbook Air (or any other notebook) is toast.
You don't buy an Ultrabook if you want durability. If you want a thin-and-light durable, you get a ThinkPad X301 or a business-class thin-and-light. They're not as thin, but you can throw it around and stand on it without too many problems.
AMD is too fat
And yet Brazos APUs (E-350/E450) still appear in tablets.
And almost all the mobile APUs (not the MX parts) are 35W parts, just like the standard power Sandy Bridge processors are. Except that they're actually competent in processor graphics whereas Quick Sync is a one-trick pony (not to discount its usefulness yet, however).
Salesman:
"Hey, these two computers are identical but this one cost $40 more because the chassis is aluminum. Of course if you get the less expensive one you can buy a nice wireless mouse too for the same total money or just save it."
Customer:
"Wow, that's a doozy, umm.......ummm..."
Intel ultrabook platform need 17W CPU. Mobile Liano is 35W which is too hot. Brazos APU has lower TDP but it is aiming cheap/low-performance market. It won't sell if using expensive ultrabook cases.
None machining i think, it's all cut and bend for fast production by presses. Carbon fiber is overkill for an laptop, unless you plan to go to war with it and use it as protection.
@steelbox
i highly doubt they would make a laptop chassis out of sheet metal aluminum (in the main presses are used in sheet metal fabrication) might work for an iPhone4 but not a laptop, it would be a pressure die cast aluminum chassis and no matter how good a process you got your still going have to do some machining for interface fit and holes
cost is rarely on material alone, fabrication time and tooling cost is a factor too, if we talking about 10's of 1000's of parts then fiber glass makes sense, but if we talking about 100's of 1000's of parts the the high cycle time for die cast aluminum becomes more cost effective
@burnley14
the chassis should never be designed as a heatsink, it's primary role is to absorb and dissipate stress loads, using it as a heat sink would diminish it's ability to handle stress loads