Abstract:  The authors study numerically the propagation of Lamb waves in one-dimensional periodic thin plates
consisting of a row of void cylinders inserted periodically in the host material.The surfaces of the plates arc parallel
to the axis of periodicity.The lowest Lamb wave complete band gap of the composite thin plates originates mainly
from the Bragg scattering and only exist in some filling ratio range.The band gap reach its maximum width almost
in the same filling ratio for the cylinder radius and lattice spacing arc respectively employed as variables. We show
that the band gap has a good adjustability and can be substantially enlarged by using multiple periodic systems which
consist of several pieces of periodic structure with different filling fraction.