Vacuum Controller for Tuneable Structured Fabric Vibration Absorbers

This paper presents the preliminary results on the design and implementation of a tunable structured fabric vibration absorber. The system is composed by a beam-like in-vacuo composite structure with a center post, whose dynamic response resembles that of a classical mass-spring-damper seismic absorber. The beam-like structure is formed by one or multiple core structured fabrics made with truss-like particles, which are coated on a sealed plastic skin. The casing skin is deflated in such a way as the particles of the fabrics jam and generate a solid structure whose bending stiffness can be tuned by adjusting the level of vacuum. To start with, the paper describes the absorber and the plant used to vary the vacuum in the sealed skin. Then, it discusses the dynamic response of the absorber with respect to measurements of the vibration transmissibility and of the base impedance frequency response functions taken at incremental levels of vacuum. Finally, it investigates the vibration control effects produced by the absorber on the resonant response of the second flexural mode of plate structure, which is excited by a white noise force. The paper shows that the prototype tunable structured fabric vibration absorber built for this study can be suitably tuned over about 8 Hz frequency range. Also, it produces about 25 dB reduction of the resonant response of the first flexural mode of the hosting plate.