Ultrasonic NDT of subsurface cracks in attenuating nanocomposite

Theoretical predictions of the specific strength and stiffness of nanocomposites make them attractive replacements for alloys and modern fiber-reinforced composites in future generations of numerous structures. The reliable and safe utilization of these nanocomposites will require their periodic evaluation with nondestructive testing. Analytical mass-spring-dashpot lattice models (MSDLM) for the ultrasonic nondestructive testing of attenuating nanocomposites containing subsurface cracks are developed. The homogenization of the elastic and viscoelastic mechanical properties of the nanocomposite constituents is implied in the use of the MSDLM. Numerical accuracy requirements restrict minimum discontinuity dimensions to 1/20 of the models' characteristic wavelengths. Full-field wave propagation simulations of these models as well as the corresponding model of a pristine nanocomposite are conducted, and their relative surface displacements are analyzed. The initial temporal and spatial disturbances of these relative surface displacements along with root mean square averages of the vertical relative surface displacement provide guidelines for characterizations of subsurface cracks and discontinuities in nanocomposites and other attenuating materials.