  We consider the problem of boundary feedback stabilization of a multilayer
Rao-Nakra sandwich beam. We show that the eigenfunctions of the decoupled
system form a Riesz basis. This allows us to deduce that the decoupled system
is exponentially stable. Since the coupling terms are compact, the exponential
stability of the coupled system follows from the strong stability of the
coupled system, which is proved using a unique continuation result for the
overdetermined homogenous system in the case of zero feedback.
