Tunable fluidic composite mounts for vibration absorption

Tuned vibration absorbers have been shown to reduce the forced vibration response at a specific frequency for many applications. This paper presents a novel absorber using fluidic flexible matrix composites (F²MC). Fiber reinforcement of the F²MC tube kinematically links the internal volume with axial strain so that fluid flows in and out of an axially vibrating tube. Coupling of an F²MC tube through a fluid port to a pressurized air accumulator produces a novel absorber that can suppress vibration at the tuned absorber frequency. A 3-D elasticity model for the tube and a lumped model for the fluid mass produce a fourth-order F²MC-mass model. The analytical closed-form isolation frequency is derived and shown to depend primarily on the port inertance, orifice flow coefficient, and the tube parameters. Viscous damping in the orifice can be adjusted to reduce the resonant peak and broaden the isolation bandwidth. With a fully closed orifice, the zero disappears and the system has a single resonant peak. For a constant port inertance, variations in the primary mass do not change the isolation frequency, making the F²MC absorber robust to mass variations. Experimental results validate the theoretical predictions by demonstrating a tunable isolation frequency that is insensitive to primary mass variation as well as a 94% reduction in forced vibration response relative to the closed-valve case at the isolation frequency.