Inflatable composite structures enable lightweight transportable buildings
May 7, 2005 Inflatable structures (aka airbeams) have developed rapidly in recent times, finding application in a variety of new engineering projects ranging from military tents in Iraq and Afghanistan to antennas in outer space. With necessity as the driving force, a team of engineers at the U.S. Army Soldier Systems Center in Natick forms the backbone of research into the technology. And the results have been spectacular - the technology has reduced the transportable weight of a tent by 66%, the transportable volume by 75% and the setup time by 50%.
Founded in 2002, the Center of Excellence for Inflatable Composite Structures headquartered at the Natick Soldier Center’s Collective Protection Directorate has managed a textile technology process to create airbeams that are lightweight and compact.
Army shelters were the first beneficiaries of airbeam technology, but the technology has transferred to the Air Force, Marine Corps, Navy and NASA with the assistance of industry partners Vertigo Inc. and Federal Fabrics-Fibers Inc.
“The technology was around, and people were working on inflatables, but there was no standard in the industry in design or performance, so we wanted all the expertise in one place to design (a customer’s) particular composite for different applications,” said Amy Soo Leighton, a chemical engineer on the Fabric Structures Team.
Leighton along with engineers Jean Hampel, Claudia Quigley and Karen Santee contribute to the design, testing and evaluation of airbeam products for the Center of Excellence, using modeling and analysis to find the optimal design.
Interest has grown in inflatable structures as they spread the word at conferences and in publications.
“We can think of a lot of applications at Natick, but others think of areas that we never expected,” Leighton said, recalling one inquiry on an airbeam design to quickly move a generator off a vehicle. “We know the technology well enough to meet their standards and have the capability in-house to design (the structures) taking into consideration safety and failure methods.”
Airbeams are manufactured by continuous braiding or weaving of a high-strength 3-D fabric sleeve to provide structural strength over an air-holding bladder. What results is a smooth, durable and seamless tube anywhere from 2-40 inches in diameter set at different pressures, depending on the support needed. Each collapsible tube has a built-in valve for a fill-up from a commercial air compressor modified with an automatic shut-off.
By changing design parameters, the airbeam shape can be modified for different products. The team guided and matured two weaving and braiding capabilities into a reliable technology with unlimited potential, according to Leighton, and in the process created an economical manufacturing base.
A project on a large shelter called the Transportable Helicopter Enclosure led to the Chemically and Biologically Protected Shelter System, which was fielded in 2003. The low-pressure system deploys connected to a Humvee and is equipped to treat contaminated patients.
Other medical shelters in development are the Future Medical Shelter System and 21st Century Military Hospital System, both designed for pre-operative and post-operative care in an environment protected against chemical and biological agents.
After a successful demonstration of the Future Medical Shelter System, the Future Combat System Medical Vehicle Treatment will be demonstrated, according to Leighton.
“Unlike how the (Chemically and Biologically Protected Shelter) is connected to a Humvee, the new system could be self-sustaining so it can be separated from the vehicle,” she said. “With photovoltaics, it could provide its own generator power to fill up with the air compressor.”
Units from Fort Riley, Kan., and Fort Bliss, Texas, are helping evaluate another type of shelter, the Small Tactical Airbeam Tent, for rapid transition of airbeam-supported shelters to the field. The Standard Integrated Command Post System also could become an airbeam-supported tent.
Similar designs were used in an exercise by the Departments of Homeland Security and Defense to protect people and unmanned aerial vehicles used by the Border Patrol, Leighton said.
The larger the scale, the larger the payoff over conventional structures, she said. The Air Force has cashed in by awarding a contract to Vertigo last June to develop the Large Shelter System, which will serve as an aircraft hangar as part of an expeditionary base.
Although shelters remain a major market for inflatable structures, airbeams are spreading into ship fenders, ejection seat stabilizers, high-glide deployable parachute wings, inflatable ladders, pollution containment booms and fuel bladders.
Miles above, NASA has applied the technology for a 60-foot inflatable airbeam extension boom for a shuttle remote manipulator system to enable astronauts to perform external in-orbit inspection and repair. The agency also is interested in inflatable antennas.
Spin-offs from the manufacturing technology include low-cost rigid composite nose cones for missiles and the next-generation chemical and biological agent-resistant laminated fabric.
For their efforts, the engineers won a 2005 Federal Laboratory Consortium Award for Excellence in Technology Transfer, which will be presented in May.
The award recognizes laboratory employees who have accomplished outstanding work in the process of transferring federally-developed technology to the marketplace. A panel of experts from industry, state and local government, academia and federal laboratory system judge nominations.