Structural and Material Characterization of Inflatable Drop-Stitch Panels Used in Bending Applications

Inflatable beams, arches and panels have become increasingly popular for load-bearing applications and have a variety of military and civil applications. The popularity of these structures comes from being lightweight, easy to transport, and being able to regain shape after the structure has been overloaded and the load is removed. The majority of inflatable beams and arches – commonly termed “airbeams” – are cylindrical pressure vessels with a circular cross-section. In contrast, drop-stitch panels incorporate yarns that connect the top and bottom surfaces, giving a wide, shallow cross-section with parallel top and bottom surfaces. Unlike airbeams, drop-stich panels do not incorporate a bladder due to the presence of drop-yarns. Therefore, the majority of drop-stich panels use a coated fabric. The primary objective of this research was to develop testing procedures to determine the constitutive properties of orthotropic neoprene/nylon drop-stitch inflatable panel fabric, and to quantify panel bending load-deflection response. This was done through panel inflation and skin coupon testing, large-scale torsion tests, and full-scale four-point bend tests. Panel inflation and skin coupon testing was done to determine the effective panel orthotropic constitutive properties in the longitudinal/warp and transverse/weft directions of the panel. Torsion testing was performed to determine the membrane shear modulus. Full-scale panel bending tests to large displacements were used to quantify panel bending load-deflection response and the effect of inflation pressure on panel stiffness and capacity. The large-scale bend test load-deflection behavior was compared to the response estimated using the experimentally-determined skin constitutive properties. The bend test results indicated that there were likely significant shear deformations in the panel during bending, which was supported by the fact that the membrane shear modulus determined from the torsion tests was a small fraction of the membrane elastic moduli. While the actual response of the panel was softer than predicted using Euler beam theory, significantly stiffer response and higher capacities were observed at higher pressures as expected. It was also observed that with an increase in pressure, there is an increase in the membrane modulus. Prior literature has observed that the pressure-volume work effectively increases the shear rigidity (Davids and Zhang, 2008) (Davids, 2009). The increase in shear modulus with inflation pressure also contributes to the increase in panel bending stiffness

Determination of biomembrane bending moduli in fully atomistic simulations.

The bilayer bending modulus (Kc) is one of the most important physical constants characterizing lipid membranes, but precisely measuring it is a challenge, both experimentally and computationally. Experimental measurements on chemically identical bilayers often differ depending upon the techniques employed, and robust simulation results have previously been limited to coarse-grained models (at varying levels of resolution). This Communication demonstrates the extraction of Kc from fully atomistic molecular dynamics simulations for three different single-component lipid bilayers (DPPC, DOPC, and DOPE). The results agree quantitatively with experiments that measure thermal shape fluctuations in giant unilamellar vesicles. Lipid tilt, twist, and compression moduli are also reported

Zero-Mode Dynamics of String Webs

At sufficiently low energy the dynamics of a string web is dominated by zero modes involving rigid motion of the internal strings. The dimension of the associated moduli space equals the maximal number of internal faces in the web. The generic web moduli space has boundaries and multiple branches, and for webs with three or more faces the geometry is curved. Webs can also be studied in a lift to M-theory, where a string web is replaced by a membrane wrapped on a holomorphic curve in spacetime. In this case the moduli space is complexified and admits a Kaehler metric.Comment: LaTeX, 17 pages, 5 eps figures; v2: references adde

Synthesis of Cellulose Acetate-Polystyrene Membrane Composites from Pineapple Peel Wastes for Methylene Blue Removal

The cellulose acetate-polystyrene or CA-PS composite membrane from pineapple peel waste for methylene blue removal has been conducted. The steps were nata de pina preparation, cellulose acetylation process, preparation, and characterization of CA-PS composite membrane. The CA-PS composite membrane was characterized using Fourier Transform Infrared (FT-IR), Scanning Electron Microscopy (SEM), tensile and strain examination, respectively. The as-synthesized CA-PS composite membrane has the characteristic of rejection ability was about 29.96% with the pore size, membrane modulus, stress and strain were 1.9 μm, 12.48 MPa, 31.91 MPa, and 2.55, respectively. In this research, CA-PS composite membrane from pineapple peel waste was successfully removed the methylene blue dye even needs improvement to enhance its capability in rejection efficiency as same as membrane characteristics.  

Simulation of Carbon Dioxide Removal by Three Amine Mixture of Diethanolamine, Methyldiethanolamine, and 2-Amino- 2-Methyl-1-Propanol in a Hollow Fiber Membrane Contactor Using Computational Fluid Dynamics

The present paper investigates the simulation of carbon dioxide removal from natural gas stream by a mixture of three amines of diethanolamine (DEA), methyldiethanolamine (MDEA), and 2-amino- 2-methyl-1-propanol (AMP) in a hollow fiber membrane contactor made from polypropylene using finite volume method (FVM). The effect of structural parameters of length and thickness of membrane and diameter of shell on the removal efficiency was studied and the optimized values were calculated. The calculations were made with the assumption of two-dimensional symmetric geometry and compared with those of three-dimensional one. The effect of number and size of the meshes on the simulation results was also studied. The simulation results were validated against the experimental values from the literature. The results imply that the increase in the length and decrease in the thickness of membrane enhances the removal efficiency. As a result, higher quantities of carbon dioxide are transferred from the shell to the membrane and amine solution inside the tube which decreases the effluent CO2 of shell and increases the average concentration of CO2 in the membrane and tube sides. The changes in effluent CO2 of shell with respect to amine solution concentration and influent CO2 indicate the insignificant influence of influent CO2 concentration on the removal efficiency

The role of traction in membrane curvature generation.

Curvature of biological membranes can be generated by a variety of molecular mechanisms including protein scaffolding, compositional heterogeneity, and cytoskeletal forces. These mechanisms have the net effect of generating tractions (force per unit length) on the bilayer that are translated into distinct shapes of the membrane. Here, we demonstrate how the local shape of the membrane can be used to infer the traction acting locally on the membrane. We show that buds and tubes, two common membrane deformations studied in trafficking processes, have different traction distributions along the membrane and that these tractions are specific to the molecular mechanism used to generate these shapes. Furthermore, we show that the magnitude of an axial force applied to the membrane as well as that of an effective line tension can be calculated from these tractions. Finally, we consider the sensitivity of these quantities with respect to uncertainties in material properties and follow with a discussion on sources of uncertainty in membrane shape

Run-Around Membrane Energy Exchanger Prototype 4 Design and Laboratory Testing

The run-around membrane energy exchanger (RAMEE) is a novel design that utilizes a membrane and a liquid desiccant to transfer heat and moisture between remotely located ducts. A laminate membrane called AY Tech ePTFE (expanded polyetrafluoroethylene) was sourced based on the vapour diffusion resistance (VDR), liquid penetration pressure (LPP), modulus of elasticity (E), and price. The measured VDR, LPP and modulus for the AY Tech. membrane were 97±11 s/m, >82 kPa, and 387±32 MPa respectively. A laboratory model of RAMEE prototype 4 was constructed using the AY Tech. membrane. The effectiveness of the laboratory model was evaluated using the energy exchanger test facility. Airstream temperatures and relative humidity’s were measured at various location to determine the exchanger effectiveness. The highest total effectiveness values measured for prototype 4, at AHRI test conditions, were 52±16% and 47±7% for a net transfer unit (NTU) of 12.3 and a NTU of 5.0 respectively