Experimental methods to determine the constitutive properties of fabric inflatable structures

In an effort to reduce deployment cost and time, the military is taking a closer look at how to more efficiently deploy and construct their shelters. In support of this effort, one current research topic is lightweight inflatable structures used for maintenance and shelter. While inflatable fabric structures are not new, recent developments have vastly improved the load-carrying capability and durability of these structures, allowing them to replace traditional framed tent structures. This is due in large part to the development of inflated structural members called airbeams, which are essentially pressurized fabric tubes with an impermeable internal bladder. The working pressures of the structural airbeams are upwards of 592 kPa. There are two major types of airbeams; woven and braided. The woven beams generally operate at lower pressures (69-296 kPa), while the more recently developed braided beams operate at much higher pressures (296-592 kPa). Since the technology of airbeams is relatively new, there are few standard material tests for determining the fabric constitutive properties necessary for airbeam design. This represents a significant barrier to their efficient implementation. This paper will present the current state of the art in relevant areas of textile testing and describe test practices useful for identifying the constitutive properties of the airbeam fabrics. In addition, preliminary testing of inflated airbeams will also be presented, and the results discussed.