Dynamics and control of micropolar material structures with embedded angular momentum

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Thirty years ago it was proposed to model structural systems that contained a very large number of gyroscopes as an elastic continuum with an embedded continuous distribution of angular momentum. The idea came from the astronautics community where the notion of very large space platforms (satellites) was popular and means of controlling their shape and orientation were of interest. Initial work established the merits of the idea for structural shape control but interest waned because these systems would not be realized owing to their cost. A new opportunity for application of this idea lies at the opposite end of the scale spectrum. Micro-Electro-Mechanical (MEMS) devices offer an unprecedented opportunity to build "smart" material systems that will macroscopically display behaviours not possible with conventional materials. With the ongoing developments in micro and nano device fabrication a material that contains an embedded, independent and controllable distribution of angular momentum could be created, should there be compelling reasons to do so. Materials with these attributes, previously referred to as gyric materials, have received scant attention but prior work has established their potential for structural shape control. This ability could be beneficially incorporated in optical devices to tune mirrors, in the active control of boundary layer behaviour in aeronautic applications, or possibly in surgical instruments where very small shape changes may be advantageous. There are many potential applications. These material models require an asymmetric stress tensor and it has been shown that material models that assume asymmetric strain and stress tensors are effective and applicable at the micron scale. Hence it is proposed that an investigation into the dynamics of material and structural systems with fundamental contributions from distributed inertial, elastic, dissipative, and gyroscopic influences be undertaken using a micropolar theory of elasticity.