Pressure → membrane demand
Explore an ideal inflated cylinder or sphere. Change pressure, radius, and thickness to compare membrane force and wall stress. Inputs describe an already-inflated shape, independently of the pattern studio mesh.
Idealized membrane view
One uniform color represents the larger analytical membrane stress. Mesh lines illustrate geometry only; they are not finite elements. The scale stays fixed when inputs change. Values above the scale maximum saturate the color.
| Direction | Membrane force · N/mm | Wall stress · MPa |
|---|
Pressure sweep
At the entered radius and thickness. The dot marks the current pressure; the line follows the larger membrane force. Changing pressure here does not expand or reshape the geometry.
How I would connect this to my sewn prototypes
Start with a tube or rounded chamber, measure its inflated radius and gauge pressure, and compare the analytical force with fabric and seam strip tests. Then record pressure, dimensions, seam behavior, and leakage during a small physical test. An arch, a junction, or an irregular inflated mesh needs a model that includes its actual geometry and restraints.
Equations, units, and model boundaries
Gauge pressure p = inside pressure − outside pressure. With p in N/mm², radius r in mm, and thickness t in mm: cylinder hoop force N₁ = pr, axial force N₂ = pr/2; sphere N₁ = N₂ = pr/2. Wall stress σ = N/t, in N/mm² = MPa. Pressure entered in kPa is divided by 1,000 to obtain N/mm².
The model assumes a thin, taut membrane in its prescribed inflated configuration, uniform thickness and pressure, and no external loading. The closed cylinder is evaluated away from end effects. Radius/thickness below 10 is flagged as outside the tool’s thin-wall screen. At zero pressure, the result is zero membrane demand; it does not imply that an unpressurized textile will hold its shape. Woven-fabric anisotropy, silicone stretch and thinning, pattern compensation, seam peel, stress concentrations, and stability require additional analysis.
What a full inflatable-structure analysis would need
A reference cutting geometry and fabric directions; measured warp/weft and shear response or a calibrated silicone hyperelastic model; seams, reinforcement, and ports; supports and anchors; gauge pressure and external loads; nonlinear pressurization and large-deformation equilibrium; and comparison with physical pressure–shape tests. Outputs should include displacement, membrane force/stress with units, support reactions, and convergence information.