Damage assessment based on general signal correlation: Application for delamination diagnosis in composite structures

This work presents a Vibration-Based Structural Health Monitoring (VSHM) technique which is developed and applied for delamination assessment in composite laminate structures. It suggests the mutual information as a measure for nonlinear signal cross correlation. The mutual information between two signals measured on a vibrating structure is suggested as a damage metric and its application for the purposes of damage assessment is discussed and compared to the application of the traditional linear signal cross-correlation. The cross correlation is capable to detect linear dependence between two signals and thus can be used for diagnosing damage on linearly vibrating structures. On the other hand the mutual information is a nonlinear metric, and it is shown that it can detect linear as well as nonlinear signal dependence and thus it is particularly appropriate for structures with nonlinear dynamic behaviour and for composite structures as such. The application of the mutual information as a damage metric is demonstrated and discussed first for the case of a simple 2 DOF system with a nonlinear stiffness. Eventually the application of the suggested damage metric is developed and demonstrated for the purposes of delamination diagnosis in a composite laminate beam.