The Navy learned its lesson concerning the use of aluminum in the construction of ships after some disastrous fires. Of course, they then promptly forgot the lesson and built the LCS out of aluminum. Now, along comes the DDG-1000 Zumwalt and the lesson may or may not have been relearned. Instead of aluminum or steel, the DDG-1000 superstructure is being built of a balsa wood core composite. Yep, wood! And glue!
The following information was taken from an article posted at compositesworld.com. (1)
The wood composite material was selected to meet fire-retardance/fire containment requirements, reduce radar and IR signature and weight, and control construction costs. Apparently, balsa burns more slowly than foam and better insulates the opposite sandwich skin from heat. The 2-3 inch wood core is sandwiched between layers of carbon fiber and vinyl ester with a stainless steel mesh integrated into the external skin, providing electromagnetic interference (EMI) shielding and a lightning ground in the otherwise nonconductive panels. The wood composite panels are being applied to the upper four levels of the superstructure (the lower three are steel) and the hangar. Similar materials were used to build the prominent pyramidal mast enclosures on the LPD-17 class.
| DDG-1000 Superstructure - Wood and Glue! |
One of the noticeable features of the Zumwalt superstructure is the large expanses of flat sides. This was apparently dictated by a desire to keep tooling and mold costs down. The wood composite panels can be as large as 120 ft long by 60 ft wide. The performance of the composite construction was verified by the construction of a 1/3-scale model of the deckhouse, which was tested at China Lake Naval Air Weapons Station in California Mojave desert .
Structural support beams are made from similar composites.
This is fascinating technology. Of course, it remains to be seen how the wood composite materials will perform in use and in combat. Can they absorb the continual flexing of a ship at sea that causes the cracks in the aluminum superstructures of the LCS and Ticonderoga classes? Will they provide any measure of protection from shrapnel? Most resins produce toxic fumes when burned – will this be a manageable problem? Will the composites provide sufficient electromagnetic transparency for the radars – there are reports that suggest that the LPD-17 class enclosed masts have such problems. Can repairs and maintenance be performed at sea?
Whether it turns out to be a success or bust, the DDG-1000 is going to be a very interesting ship to watch over the next several years.
(1) http://www.compositesworld.com/articles/ddg-1000-zumwalt-stealth-warship, DDG-1000 Zumwalt: Stealth warship - U.S. Navy navigates radar transparency, cost and weight challenges with composite superstructure design, Michael R. LeGault, 1/18/2010 , Source: Composites Technology