MECHANICAL RESPONSE OF WATER-FILLED DROP-STITCH INFLATABLE STRUCTURES

Inflatable structures are essential for a wide variety of applications due to their lightweight and high stiffness capabilities. Having a low storage volume, they can quickly be pressurized to produce a rigid and rapidly deployed structure. Due to their increasing popularity, research on air-inflated drop-stitch structures is becoming more common. However, little work has examined liquid-inflated structures. There are unresolved questions about the effect that liquids have on the materials and a lack of engineering data for designing components that are to be pressurized with a liquid. The objective of this research is to determine the mechanical response of a water-filled drop-stitch inflatable panel. Drop-stitch panels can be manufactured with several different materials and construction methods. The panel evaluated in this research is commercially manufactured with a PVC-laminated, knitted fabric material. Using both air and water to pressurize the panel, inflation tests and three-point bend tests were conducted for each inflation method, then compared. Classical beam theory was used to model beams in three-point bending. For the inflation tests, average strain values were determined with three-dimensional digital image correlation up to 10 psi. Results show increased strain in the skin when inflating the panel with water. For the three-point bend tests, the panel was tested at 5, 7.5, and 10 psi, and the weight of the water was treated as a uniform load. The theoretical deflection due to superposition of the uniform load and the concentrated mid-span load is compared to the deflection that was obtained experimentally. The results of this research suggest that inflating a panel with water results in a slightly higher bending stiffness as compared to an air-inflated panel