Riesz Basis Property and Related Results for a Rao-nakra Sandwich Beam

We consider a three layer Rao-Nakra sandwich beam with distinct wave speeds. We prove that the eigenvectors form a Riesz basis for the natural energy space. In the damped case, we give precise conditions under which there is a uniform exponential decay of energy. We also consider the problem of boundary control using bending moment and lateral force control at one end. We prove that the space of exact controllability has finite co-dimension and provide sufficient conditions (related to small damping) for exact controllability to a zero energy state.