Numerical Modelling of Propagation of the Fundamental Symmetric Lamb Mode through a Metal Composite Adhesive Joint

The interaction of the fundamental S0Lamb mode with adhesive joint considered between GFRP composite laminate and aluminium was studied through numerical modelling carried out using FEM. The numerical simulations were carried out by exciting the fundamental A0 Lamb mode at metal end in the frequency range of 150-225 kHz by varying the adhesive orientation in the range of 1 in 20 to 900.When S0 Lamb mode interacts with adhesive, reflection, transmission and generation of A0 takes place. The incident S0 and generated A0 modes propagate in the model as S0S0 and S0A0 modes. The ToF of reflected and transmitted S0S0 and S0A0 modes at receiving points were calculated analytically and compared with those obtained from numerical simulations.Further, RF and TF of Lamb modes S0S0 and S0A0 propagating through the sample were estimated. It is observed that, RF and TF values are depending on the adhesive orientation and the excitation frequency. The detailed study on variation of RF and TF was made by exciting at metal and composite end with excitation frequency in the above range. Further, It was found that, scattered (transmitted and reflected) S0S0 and S0A0 Lamb modes are sensitive to the adhesive and hence, it can be used for detection of disband in metal-composite adhesive joint