Vibration response of in-vacuo tuneable structured fabrics

This paper presents a first survey on the vibration response of beam-like specimens formed by a vacuum plastic bag with single-layer or double-layer 3D-printed structured fabrics encompassing spherical-octahedra, octahedra and cubes trusslike rigid elements. The study reports a comprehensive analysis of the bending stiffness and energy dissipation properties with respect to the level of vacuum as well as the type and number (single or double) of overlapped fabrics. In this context, it first presents a quasi-static analysis of the bending stiffness and energy dissipation of the specimens. Then, it provides a comprehensive overview of the specimens dynamic properties with respect to measurements of the dynamic stiffness frequency response function and with reference to measurements of hysteresis loops at three characteristic frequencies, namely below, at and above the fundamental bending resonance frequency of the beam-like specimens. The study shows that the bending stiffness and thus the fundamental bending resonance frequency of the specimens can be suitably varied by increasing the level of vacuum in the bags. The specimens made with cubic mails show the highest bending stiffness and fundamental resonance frequency. Also, the specimens with double layer mails show much higher bending stiffness and fundamental resonance frequency. The level of vacuum has little effect on the energy loss, which, in general, is characterised by rather low loss factors. This suggests that once the fabric jams, there is little friction between the particles and the principal damping mechanism is offered by the material energy dissipation in the unit particles.