Less than a decade ago the U.S. Navy invested in metal ships and purchased small composite components for mine hunters and airplanes. In 2008, everything changed. Now the U.S. Navy is investing in the largest composite parts in the world—and Huntington Ingalls (HII) Gulfport Composite Center of Excellence is the harbinger of composite navy giants.
In February 2008, the U.S. Navy contracted Northrop Grumman to construct the deckhouse of the DDG 1000 destroyer for $1.4 billion. Composite panels were chosen to provide material savings, corrosion and sonar resistance, and remove topside weight. Northrop Grumman took advantage of the composite technology at the Gulfport facility, now known as Huntington Ingalls Gulfport Composite Center of Excellence, located in the coastal town of Gulfport, Miss. In the past few years, the Gulfport facility has developed a technique for curing large composite panels using vacuum assisted resin transfer molding (VARTM) in significantly less time than traditional methods.
Originally, the VARTM process took over 24 hours to cure the large panels—today the process takes under 13 hours. “At first we had problems with race tracking, where the resin would scoot around sharp corners of the mold table and miss the cloth. But our technicians learned from these mistakes,” says Jay Jenkins, plant manager at the Gulfport facility. “After years of trial and error with the process, we were able to produce panels in half the time we started. The second DDG 1000 ship was completed well before schedule.”
The composite laminated parts for the DDG 1000 program are roughly the size of conference tables, using balsa wood, T-700 carbon fiber and a brominated resin (a fire-retardant organobromide resin) to meet Navy fire code standards. It takes roughly 20-30 sub-assemblies to build one composite panel. The deckhouse spans 160 feet in length and is 70 feet wide by 65 feet high, taking up a huge corner of the facility when under construction.
The biggest challenge that the company faced during the DDG 1000 project was handling the pure size of the composite parts. After manufacturing and joining all the panels, HII must test over 25 million square inches of joints. To overcome this challenge HII invented a new ultrasonic transducer for large structures. “It’s basically a sled that incorporates transducers and computer software to take an ultrasonic picture of the parts. We walk that sled from end to end on overlapping paths and scan the deck in a number of hours rather than days or weeks,” says Jenkins.
Recently HII signed a new contract to construct the final DDG 1000 and build two smaller DDG 51 Arleigh-Burke Missile-Guided Class destroyers, the DDG 51 design was recently updated to replace steel with similar composite technology in the mast to reduce radar signature. Jenkins also believes that composites could solve the Navy’s problems with cracking in aluminum stacks and deckhouses.
According to Jenkins, even more exciting projects are in the pipeline. Determined to use the VARTM technology on other large structures, HII is investigating new uses in the wind energy, oil and other commercial sectors. “We’re not tied to work in this area. As we look at other jobs and bring others in, we can adjust the space at our facility to accommodate different jobs,” says Jenkins. Jenkins expects that composites will have to fight for further integration against established metals but believes firmly that composites are the best building material for the future of the U.S. Navy.