Membrane Mechanics of Pressurized Cylindrical Shells

Flexyshell uses the fundamentals of membrane mechanics to transform how high-pressure vessels work. Unlike traditional rigid-walled tanks, which develop dangerous compressive and bending stresses at their inner walls, Flexyshell adopts a flexible cylindrical wall that manages internal pressure through hoop tension alone. This novel approach minimizes harmful stress concentrations and allows minor self-recovering deformations—so the vessel safely returns to its shape even after extreme events, providing superior resilience for high-pressure hydrogen storage.

Pressure-Induced Stiffening and Structural Stability

Internal pressure does more than just contain gas—it stabilizes the flexible wall itself. When the wall is pressurized, it becomes geometrically stiff, resisting ovalization and maintaining its cylindrical shape even under bending or side loads. This pressure-induced stiffness allows the structure to carry external loads through in-plane tension rather than through bending or local compression.  Supported by a wealth of aerospace research, Flexyshell extends these principles to ultra-high pressures, using specially designed external tendons and dome systems architecture to offload axial stresses. This ensures the vessel consistently behaves as a tension-dominated structure, dramatically improving performance up to 1000 bar.

Safe Absorption of External Loads

Flexyshell is designed so that external forces—lateral, bending, point impacts—are absorbed and redistributed as safe tensile fields:

• Bending or Lateral Loads: The shell acts like an inflated beam, shifting force toward areas able to carry tension and away from zones vulnerable to compression.
• Point Impacts: Elastic deformation and tension redistribution help prevent brittle failures typical of rigid composite tanks, such as delamination or microbuckling.
• Axial Loads: Tendons through the proprietary end architecture absorb these forces, keeping the cylindrical wall purely in hoop-tension.

This mechanism ensures all service loads (pressure, external bending, impact) resolve through controlled, damage-tolerant tension fields.

Wrinkle Initiation and Reversibility: Built-In Safety

When pressurized membrane cylinders are bent, local wrinkles can form if the load is extreme—much like an inflatable airbeam. However, these wrinkles are not failure points. Experiments show that wrinkles only initiate at high loads, remain localized, and the structure can carry up to 1.8 times more load before collapse, even after wrinkle has formed. After removing the load, the vessel returns to its original shape without damage or loss of capacity. This tension-field response is fundamentally safer than the sudden, catastrophic failure modes of rigid composites.

Historical Precedent and Innovative Application

Decades of research in aviation and aerospace—like NASA’s experiments with inflatable cylinders—prove that pressurized membranes can provide significant structural strength, even at low pressures. Flexyshell builds on this foundation and brings it to new heights, applying the design principles at unprecedented pressures for hydrogen storage and marine modules. The combination of pressure-stiffened flexible walls and external tendon support offers unmatched safety, resilience, and scalability.

Goodyear Inflatoplane—an experimental aircraft demonstrating load-bearing capabilities of pressurized flexible membranes at only 0.5 bar internal pressure. Its successful flights highlight the fundamental principle behind Flexyshell technology.