  The study of elastic structures embedded with fluid-filled cavities received
considerable attention in fields such as autonomous materials, sensors,
actuators, and smart systems. This work studies an elastic beam embedded with a
set of fluid-filled bladders, similar to a honeycomb structure, which are
interconnected via an array of slender tubes. The configuration of the
connecting tubes is arbitrary, and each tube may connect any two bladders. Beam
deformation both creates, and is induced by, the internal viscous flow- and
pressure-fields which deform the bladders and thus the surrounding solid.
Applying concepts from poroelasticity, and leveraging Cosserat beam
large-deformation models, we obtain a set of three coupled equations relating
the fluidic pressure within the bladders to the large transverse and
longitudinal displacements of the beam. We show that by changing the viscous
resistance of the connecting tubes we are able to modify the amplitude of
oscillatory deformation modes created due to external excitations on the
structure. In addition, rearranging tube configuration in a given bladder
system is shown to add an additional degree of control, and generate varying
mode shapes for the same external excitation. The presented modified Cosserat
model is applied to analyze a previously suggested energy harvester
configuration and estimate the efficiency of such a device. The results of this
work are validated by a transient three-dimensional numerical study of the full
fluid-structure-interaction problem. The presented model allows for the
analysis and design of soft smart-metamaterials with unique mechanical
properties.
  Keywords: autonomous materials, adaptive materials, programmed materials,
smart systems, autonomous systems, soft matter, soft robotics, energy
harvesting, fluid dynamics, fluid-structure interaction, large deformation.
