Fluidic Flexible Matrix Composite Vibration Absorber for a Cantilever Beam

Abstract

Fluidic flexible matrix composite (F2MC) tubes with resonant fluidic circuits can absorb vibration at a specific frequency when bonded to flexible structures. The transverse structural vibration applies cyclic axial strain to the F2MC tubes. The anisotropic elastic properties of the composite tube amplify the axial strain to produce large internal volume change. The volume change forces fluid through a flow port and into an external accumulator. The fluid inertance in the flow port (inertia track) and the stiffness of the accumulator are analogous to the vibration absorbing mass and stiffness in a conventional tuned vibration absorber. An analytical model of an F2MC-integrated cantilever beam is developed based on Euler–Bernoulli beam theory and Lekhnitskii's solution for anisotropic layered tubes. The collocated tip force to tip displacement analytical transfer function of the coupled system is derived. Experimental testing is conducted on a laboratory-scale F2MC beam structure that uses miniature tubes and fluidic components. The resonant peak becomes an absorber notch in the frequency response function (FRF) if the inertia track length is properly tuned. Tuning the fluid bulk modulus and total flow resistance in the theoretical model produces results that match the experiment well, predicting a magnitude reduction of 35 dB at the first resonance using an F2MC absorber. Based on the experimentally validated model, analysis results show that the cantilever beam vibration can be reduced by more than 99% with optimally designed tube attachment points and flow port geometry.