Mechanics of Air-Inflated Drop-Stitch Fabric Panels Subject to Bending Loads

Abstract

Rapid deployment and mobility of lightweight structures, namely inflatable structures, are of growing significance to the military and space communities. When deployment and rigidity are driven by pressure (for example, air or fluid) and materials such as textiles, elastomers and flexible composites are used, significant load carrying capacity per unit weight (or per-unit stowed volume) can be uniquely achieved. Specifically, the pressurized air directly provides the stiffness to support structural loads, thus eliminating the requirement for heavy metal stiffeners that are used in conventional rigid structures. However, the material and system behaviors are not sufficiently understood. Furthermore, predictive-performance analysis methods and test standards are not adequately established because the behaviors of inflatable fabric structures often involve coupled effects from inflation pressure such as fluid-structure interactions (FSI’s), thermo-mechanical coupling and nonlinear constitutive responses of the materials. These effects can restrict the use of conventional design, analysis and test methods. This research explores the mechanics of air-inflated drop-stitch fabric panels subject to bending loads using analytical and experimental methods. Results of experimental four-point bend tests conducted at various inflation pressures are used to validate the analytical method. The predicted and experimental deflections, wrinkling onset moments, ultimate loads, pressure changes, etc. are compared and discussed.

The High Capacity Expanding Lifeboat HiCEL – Meeting the Modern SAR Challenge

“…This would ensure that it would not buckle (or wrinkle) under the loads it would be subjected to. The stiffness of drop stitched material is comparable with that of a composite sandwich panel (Cavallaro, Hart, & Sadegh, 2013).…”

“…One interesting feature of any inflatable structure is the propagation of wrinkles, which is a phenomenon that occurs during bending of a panel, when the tension in one skin reduces to zero (Cavallaro, Hart, & Sadegh, 2013). Wrinkle propagation is elastic in nature and there are no lasting effects on the strength of the drop stitched fabric after use.…”

Conceptual Inflatable Fabric Structures for Protective Crew Quarters Systems in Space Vehicles and Space Habitat Structures

“…Model details such as drop-stitch material properties, skin thicknesses, drop-yarn cross-sectional areas and areal densities (number of drop yarns per unit area), and methods of inflation were leveraged when possible from a prior study. 13 Displacement boundary conditions were implemented based on expected operational restraints. The woven air beams and drop-stitch skins were modeled as isotropic membranes; the drop yarns were modeled as tension-only string elements.…”

“…Advancements such as high-performance fibers and fabrics, three-dimensional (3-D) continuous-woven architectures, protective and flexible coatings, multi-axial material-level testing, and predictive-performance-analysis methods that enable virtual design processes [1][2][3][4][5][6][7][8][9][10][11][12][13] are key technological enablers for achieving new, unprecedented applications for inflatable and deployable structures that can be designed as alternatives to traditional rigid structures.…”

Mechanics of air-inflated 3D distance fabric

“…Some research on inflatable fabric structures was performed earlier but only a few on distance fabric panels [5]. Cavallaro in [2] described the mechanics of a panel loaded by four point bending load. He used experimental data of material tests for his analytical model and performed also experiment of bended panel for comparison.…”