New method employing the electrical impedance for monitoring mechanical damage evolution in glass-reinforced: Applications to riveted joints

This paper presents a new methodology to monitor the mechanical damage progression of GLAss-REinforced (GLARE) fiber metal laminate material, complementing mechanical testing. The methodology is based on assuming GLARE as a capacitor, where two consecutive aluminum layers are separated by nonconductive glass fibers embedded in polyester cloth, acting as a dielectric. The electrical impedance of the capacitor is measured in a range of frequencies during material in service operation. The methodology was validated on riveted joints in superstructures of a naval construction. Uniaxial tensile and three point bending tests were performed while simultaneously acquiring the electric parameters of the capacitor. Merging mechanical and electrical information it was possible to identify the functional mechanical resistance of the joints which is the starting condition for galvanic corrosion occurrence and this was found to take place before mechanical fracture starts. The methodology can be applied both in Structural Health Monitoring (SHM) of riveted joints in GLARE and for analyzing the material integrity, under several working conditions, including fatigue.