Wave propagation in beam-like in-vacuo tuneable structured fabrics

In-vacuo tuneable structured fabrics represent an innovative class of smart materials capable of modulating their mechanical and dynamic properties through controlled confinement pressure. When arranged in beam-like configurations, these structures can operate as vacuum-controlled waveguides with pressure-dependent stiffness and dispersion characteristics. This paper presents a preliminary investigation of elastic wave propagation in a beam-like vacuum-controlled tuneable structured fabrics under variable confinement pressures. A prototype was designed and fabricated to assess both the technical feasibility and manufacturability. Experiments were conducted using a correlation-based wavenumber identification technique to characterise wave behaviour. A one-dimensional wave finite element model was implemented in COMSOL Multiphysics, employing Floquet boundary conditions and Hertzian contact theory with a scaling factor to account for contact multiplicity. Computed dispersion curves at 20 kPa and 80 kPa confinement pressures show qualitative agreement with experimental measurements. Results demonstrate that increasing confinement pressure enhances structural stiffness and shifts dispersion branches toward higher frequencies. Wave mode shape analysis confirms multiple bending and longitudinal modes consistent with classical beam theory. These findings suggest that in-vacuo structured fabrics could provide a new means for the development of programmable metamaterials for vibration control.