The estimation of the damping coefficient may help to improve the damage detection in composite materials. The purpose of this study was to develop the simulated Lamb wave propagation method for nondestructive monitoring of matrix cracking in laminated composites via the accurate estimation of their damping coefficient. Cross-ply composite specimens with different crack densities were fabricated and tested by the Lamb wave propagation technique. The phase velocity of the Lamb wave and the damping coefficient of the specimens were measured. The finite element models were developed at micro-scale (representative volume elements) and macro-scale (laminated specimens) levels to simulate the Lamb wave propagation in composite specimens. An optimization process was performed through the model updating procedure to achieve finite element models that were in good agreement with experiments. The phase velocity and damping coefficient, obtained from the updated FE models for two crack densities other than those used in the model updating procedure, were successfully examined by experimental results. It was also revealed that the damping coefficient and the rate of increase in the damping coefficient in terms of the crack density were higher for the composite laminates with a higher number of 90° layers. The damping of the fiber–matrix interphase and crack regions were considered in the model and shown as a significant contribution to the overall damping of the composite specimens. The proposed simulated Lamb wave propagation method can be used as a virtual lab for in-situ monitoring of laminated composites with different material properties, stacking sequences, and crack densities.
Lamb Wave Propagation and Material Characterization of Metallic and Composite Aerospace Structures for Improved Structural Health Monitoring (SHM)
