Monitoring of Bonding Quality in CFRP Composite Laminates by Measurements of Local Vibration Nonlinearity

In this paper, an approach based on measurements of a local nonlinear response of the laminate is suggested and applied to monitoring contaminations of adhesive bonding in carbon fiber-reinforced polymer (CFRP). It is shown that a contaminated boundary layer of the adhesive contributes to an overall nonlinear response of the laminate that enables to evaluate and quantify bonding quality caused by various types and levels of single contaminations. All kinds of contaminations studied in the context of aviation applications result in enhancement of the nonlinear response of the CFRP laminate which is an indication of deterioration of bonding quality. The enhancement of nonlinearity in weaker bonds was also applied to imaging of the contaminated adhesion areas in realistic airplane components.