  An asymptotically exact first-order shear deformation theory for functionally
graded elastic plates is derived using the variational-asymptotic method. As an
application, an analytical solution to the problem of wave propagation in a
sandwich plate is found in accordance with this refined theory. Comparison
between the dispersion curves obtained by 2-D plate theory and 3-D elasticity
theory reveals that the former is accurate up to the order of h^2/l^2, where h
is the plate thickness and l the wavelength.
