Inverse methods for quantitative assessment of delamination damage based on vibrational response

A novel two-step approach for quantifying laminar damages, such as delaminations in composites, is presented. This new approach first employs the gapped smoothing method to locate the edges of damage from the vibrational curvature data, followed by an inverse method to determine the through-thickness location of delaminations that provide the best match with the local reduction in bending stiffness over the damaged region. Practical aspects of the implementation of this procedure are discussed, and the approach is demonstrated using both simulated and experimental data. The role of sample spacing on the accuracy of damage location is investigated systematically and it is shown that an optimum spacing exists for experimental data containing noise. The inverse method is found to be able to provide detailed information of delaminations when the searching space is limited, and it can also be used to determine the effective flexural stiffness for complex delamination damage.