Reconstruction of the nine stiffness coefficients of composites using a laser generation based imaging method

Reconstruction of the nine stiffness coefficients of two different composites was implemented by inverting the measured Lamb waves phase velocities. The inversion was carried out through genetic algorithms (GAs) by minimizing the error between the calculated and the measured velocities. Forward problem of calculating phase velocities for a material properties individual in GAs was solved using a third-order shear deformation theory (ToSDT). Lamb wave propagation was visualized with a laser generation based imaging (LGBI) system which uses a laser source to generate ultrasonic waves. The experimental phase velocities were evaluated directly based on the position-time diagrams of Lamb waves. The nine stiffness coefficients were reconstructed using phase velocities of S0 mode and A0 mode measured along only three propagation directions. The reconstructed material properties were verified by comparing their corresponding theoretical velocities with the experimentally measured velocities.