Selective mode excitation of Lamb wave in composite laminates

Lamb wave has a great potential for structural health monitoring of large area structures due to its long range propagation. The piezo array configurations and array pitch for selective mode excitation are first studied with 2D FE models in a composite plate. A single PZT actuator bonded on the top surface of the laminate in unimorph configuration excites both symmetric mode (S0) and anti-symmetric mode (A0). The A0 mode is predominant and four times stronger than the S0 mode. The second configuration is a bimorph where the PZT actuators are bonded on either side of the laminate. The in-phase excitation of PZT actuators suppress the A0 mode and excite only the S0 mode, while the out-of-phase excitation eliminates the S0 mode and launches the A0 mode in the laminate. The third configuration is the unimorph array configuration where PZT actuators are bonded on the top surface of the laminate. By keeping the array pitch equal to half wavelength of the S0 mode, the S0 mode gets suppressed by twelve times. The FE results are checked with experiments.