Multi-scale damage state estimation in composites using nonlocal elastic kernel: An experimental validation

In recent years early detection of structural damage (detecting incubation of damage) has received great attention in the structural health monitoring field. However, extraction of lower scale information to quantify the degree of damage is a challenging task, especially when the detection is based on macro-scale acoustic wave signals. All materials exhibit dependence on the intrinsic length scale. An attempt is made in this paper to extract lower scale feature from the macro-scale wave signal using nonlocal elasticity theory. The Christoffel solution has been modified using nonlocal parameters. The dispersion curves are generated for anisotropic solids using perturbation parameter through nonlocal theory. Dispersion curves are sensitive to initiation of damage in anisotropic solids at the intrinsic-length scale. In this paper detection of initiation of damage in a 4 mm carbon composite plate is demonstrated by employing nonlocal perturbation parameter and formulating a new Nonlocal Damage Index (NDI). The nonlocal theory is used to demonstrate the early prediction of failure of the system and to show progressive evolution of the damage.