Abstract
Composite structures and materials find widespread applications across industries such as civil engineering, automotive, and aerospace owing to their exceptional strength-to-weight ratio, stiffness, and resistance to corrosion. However, these materials are prone to various forms of damage, including matrix cracking, delamination, and fiber breakage, which can compromise their performance and lead to failure. Hence, the development of robust health monitoring and inspection (HMI) techniques is imperative for the multi-damage detection and durability assessment of composite structures and materials. Electromechanical impedance (EMI) emerges as a promising HMI technique for such applications. EMI, a non-destructive testing (NDT) method, involves measuring the electrical impedance of a piezoelectric sensor bonded to the structure, enabling detection and characterization of damage. In this study, standard cube specimens were cast using OPC cement, Class F fly ash, and polypropylene fiber mixture. Analysis revealed a direct correlation between the Root Mean Square Deviation (RMSD) index and crack dimensions, with heightened sensitivity observed at smaller patch-to-damage distances. Moreover, the conductance and susceptance signatures consistently shifted with increasing damage, with significant leftward shifts indicating damage severity. A new damage index, ranging from 0 to 1, facilitated quantitative damage analysis, exhibiting pronounced variation in the 30–400 kHz frequency range. Additionally, equivalent stiffness and damping structure parameters were evaluated. Overall, the research demonstrates the effectiveness of surface piezoelectric sensors based on the EMI technique in monitoring concrete damage and its evolution, providing valuable insights for predicting the service life and durability of concrete structures.