Navy gradually embracing composite materials in ships.

• Author: Tiron, Roxana

The U.S. Navy gradually plans to incorporate composite materials into the construction of new ships. Although experts agree that composites offer lighter-weight materials chat are easier to maintain, the Navy has been wary to pay the higher cost, arguing that traditional materials such as steel can do the job, are less risky and more affordable.

Nevertheless. the Navy claims that its next generation destroyer, the DD(X), will be the service's first major commitment to composite construction. Northrop Grumman Shipbuilding Systems, the DD(X) prime contractor, is beginning work on a composite deck-house.

In its selection for the Littoral Combat Ship, the Navy eliminated Raytheon's design--based on the Norwegian Skjold ship with a composite hull. A senior Navy official told National Defense that the decision does not mean the service is being too "conservative" and walking away from composite ships.

During the selection process, some speculated that a fire, which destroyed the composite Norwegian minesweeper Orkla two years ago, would play a part in the Navy's consideration.

The official argued that the two selected designs, by the General Dynamics and Lockheed Martin teams, have composite elements.

"Composites have gained more clout in the past decade, but they have been used in and on Navy platforms since the 1940's when the U.S. Navy pioneered the use of fiberglass composites for small boats, said Gene Camponeschi, program manager for composites research at Naval Surface Warfare Center at Carderock, Md. Since then the Navy has used composite materials for the MHC 51 class of mine-hunters and submarine bowdomes.

Secondary applications now being made with composites include rudders, propellers, stairways, handrails, valves and armor.

Among the most complex are the composite mast-enclosures on the San Antonio-class amphibious ship, the LPD 17.

The Navy's main reasons to use composites on its ships are the reduction in maintenance and weight, said Richard Vogelsong, a scientist at the Office of Naval Research.

Composites generally arc made out of two or more different materials combined to form a single structure with an identifiable interface. One of the earliest known composite materials is the adobe brick in which straw--a fibrous material--is mixed with mud or clay--an adhesive with strong compressive strength.

Composite materials are stronger and stiffer than metal, and for the same strength are lighter than steel and aluminum. They also...