Identification of matrix cracking in cross-ply laminated composites using Lamb wave propagation.

The purpose of the present study is to develop a nondestructive evaluation method and propose a model-independent viscoelastic characterization approach for the identification and classification of the matrix cracking in polymeric composites using the Lamb wave propagation method. To this end, cross-ply laminated composite specimens were fabricated and matrix cracking with different crack densities was induced in specimens using a tensile testing machine. The crack density was first measured by an optical microscope and compared with that of predicted by the Hashin model. Then, the fundamental anti-symmetric Lamb wave (A 0) at a frequency of 206 kHz was propagated in specimens using an ultrasound actuator and an ultrasound probe to obtain the characteristics of the induced waves including the displacement phase and the amplitude at different locations of the specimens along the propagation direction. Then, the corresponding inverse Lamb wave propagation problem was solved and the elastic and viscoelastic properties of specimens were estimated. The elastic modulus measured by the present method was in good agreement with the results obtained by an optical microscope and predicted by the Hashin model. The viscoelastic properties of specimens also showed good sensitivity to the severity of the induced matrix cracking. [ABSTRACT FROM AUTHOR]