Fatigue Damage Monitoring Of Composite Materials Through Electrical Measurements: An Analytical Framework

Abstract

Abstract

In recent years, composite materials have assumed a crucial role in advanced engineering sectors such as automotive, aerospace, and wind energy, owing to their outstanding specific mechanical properties. However, composite components subjected to cyclic loads experience a progressive degradation of their mechanical performance due to the accumulation and interaction of multiple damage mechanisms, including off-axis cracking, delamination, and fibre breakage. Consequently, continuous monitoring of the structural integrity of such components is essential in order to enable timely intervention when the functional requirements defined at the design stage are no longer satisfied. In the case of electrically conductive laminates, Structural Health Monitoring (SHM) can be effectively achieved through electrical methods, as damage phenomena induce detectable changes in electrical conductivity. This work presents an analytical framework capable of accurately describing damage evolution and the associated stiffness degradation in multidirectional conductive laminates affected by off-axis cracks and delamination in multiple layers, using the increase in electrical resistance as input parameter. The accuracy of the proposed framework is first assessed through comparison with finite element analyses, demonstrating excellent agreement. Furthermore, fatigue tests are conducted on CNT-modified quasi-isotropic GFRP laminates, with continuous monitoring of damage evolution, stiffness degradation, and electrical resistance variation. The experimental results closely match the analytical predictions, thereby confirming the accuracy of the framework and demonstrating its effectiveness as a reliable tool for the Structural Health Monitoring of composite materials.