Plate-mode waves in phononic crystal thin slabs: mode conversion.
We have computed the dispersion curves of plate-mode waves propagating in periodic composite structures composed of isotropic aluminum cylinders embedded in an isotropic nickel background. The phononic crystal has a square symmetry and the calculation is based on the plane-wave expansion method. Along GammaX or GammaM directions, shear-horizontal modes do not couple to the Lamb wave modes which are polarized in the sagittal plane. Whatever the direction of propagation in between GammaX and GammaM, shear-horizontal modes convert to Lamb waves and couple with the flexural and dilatational modes. This phenomenon is demonstrated both through the mode splitting in the lower-order symmetric band structure and through the calculation of all three components of the particle displacements. The phononic case is different from the pure isotropic plate case where shear-horizontal waves decouple from Lamb waves whatever the direction of propagation.
Institut des NanoSciences de Paris, CNRS (UMR 7588), Université Pierre et Marie Curie, 140 rue de Lourmel, 75015 Paris, France.
Jiu-Jiu
JJ
Chen
Bernard
B
Bonello
Zhi-Lin
ZL
Hou