Structural health monitoring of CNT-modified glass fiber/epoxy laminates via electrical measurements

Fiber-reinforced polymers (FRPs) have become essential materials for advanced applications, given their lightweight and high mechanical properties. However, their performance is compromised by intrinsic damage during in-service life. Electric potential-based methods offer an effective solution for monitoring damage accumulation and stiffness reduction of composite materials. In this work quantitative experimental data linking the presence of damage in a composite laminate to a variation in its electrical conductivity are produced. Such data are essential to validate predictive model proposed by the authors, that accurately predict the stiffness reduction in conductive cross-ply laminates as a function of the electrical resistance change of the laminate itself. The material system chosen consists of glass fiber/epoxy resin [0/90]s laminates, made electrically conductive through the addition of Carbon Nanotubes (CNTs). Both static and fatigue tests are carried out, monitoring the progression of damage, through visual inspection and digital image correlation (DIC). Simultaneously, electrical resistance and stiffness loss are closely monitored throughout the testing process.