In order to address stability, transportation and energy issues with rigid wall shelters, the U.S. Army’s Medical Support Systems Program Management Office (MSS PMO) will use a carbon composite retrofit kit to refurbish the current shelters and address the problems.
The rigid wall shelters are used for the core parts of Army field hospitals, housing the operating room, and the research laboratory, where the floor must be stable and free of vibration.
As the Army explains, a rigid wall shelter starts out as a container that is 20 feet long, 8 feet high, and 8 feet wide and unfolds to shelter that is triple that size, providing a floor, a ceiling and four walls. It is a very efficient design, and can be set up in less than an hour. However, because the shelter is made of aluminum, it has a number of weaknesses.
“Carbon composite is two times stiffer and, overall, the shelter will be 20 percent lighter than the current aluminum design,” said Richard O’Meara of Core Composites, which collaborated with the U.S. Army Tactical Shelters Team, and Army Natick Soldier Research, Development & Engineering Center on the upgraded composite shelters.
The retrofit kit includes a single fixed floor with two expandable floors. Because they are made with CFRP, they have double the stiffness of the previous floors, which makes them less susceptible to vibration. The kit also contains four vertical corner posts fabricated out of CFRP. Each post only weighs 50 pounds, as opposed to the current aluminum posts, which weigh 71 pounds each.
The Army says that currently, each aluminum corner post is designed to support 100,800 pounds. The composite corner posts are designed to meet strict transportation standards, which require each corner post to support 211,675 pounds in order to withstand the weight of eight shipping containers. The Army notes that increased capability improves transportation efficiency and will reduce the cost of shipping. Composites also lower the overall empty shelter weight by several hundred pounds, allowing the Army to increase the amount of cargo the shelter can carry. O’Meara adds that the composite posts are also much more corrosion-resistant than the current aluminum posts.
According to Jaime Lee, MSS PMO product manager, the Army will use FY16 funding to retrofit 24 shelters in FY17. Lee says the number of shelters retrofitted after that will come down to how cost effective the project is.
“We are procuring the kits now as an engineering change proposal to the original shelter,” said Lee. “In two years, we will reassess and do a cost-benefit analysis to see if we should just replace the entire shelter with a carbon composite shelter. It might be just as cost-effective to stay with the kit.”