Although the U.S. Navy’s new, nearly $4 billion (USD) Zumwalt-class destroyer has a steel hull, it is topped with an all-composite deckhouse superstructure that cuts topside weight and gives the ship stealth capability by reducing its radar signature. Built by Huntington Ingalls Industries (Gulfport, Miss.), the superstructure features flat sandwich panels of balsa core (Alcan Baltek Corp., Northvale, N.J.) between faceskins of T700 carbon fiber (Toray Carbon Fibers America Inc., Flower Mound, Texas) woven by Sigmatex Inc. (Benecia, Calif.) and infused with vinyl ester resin from Ashland Performance Materials (Dublin, Ohio).
The balsa-cored panels offered good fire performance, compared to foam- or honeycomb-cored alternatives, for the majority of the superstructure, but when the Navy expressed concern about the fire-readiness of its roof, more robust fire-resistant panels were developed by phenolic laminate specialist DuraSip LLC (Union, Miss.), a subcontractor to Navy contractor Temeku Technologies Inc. (Herndon, Va.), to meet the Navy’s fire code. DuraSip’s CEO and composites engineer Max Ware says the 2-ft by 2-ft by 1.5-inch thick (0.62m by 0.62m by 34-mm) panels were produced with multi-ply reinforced phenolic skins bonded to rigid phenolic foam under heat and pressure, using a phenolic adhesive. DuraSip used Momentive Specialty Chemicals Inc.’s (Columbus, Ohio) trademarked Cellobond J2027L phenolic resin, supplied through Mektech Composites Inc. (Hillsdale, N.J.). “Fiberglass or carbon fiber-reinforced phenolic laminates maintain structural properties at elevated temperatures better than laminates made with any other thermoset resin,” he comments. “Also, they give off the least amount of toxic gasses compared to other thermosets, so the phenolic panels were the right choice.” They also act as thermal insulators, to help keep the deckhouse interior at a comfortable temperature.
The roof panels, totaling 6,000 ft2/557m2, were bonded to the deckhouse with either adhesives or mechanical fasteners, and the phenolic laminate surfaces received a weatherproof coating after assembly.