Self-monitoring of composite structures strengthened with prestressed hybrid fiber-reinforced polymer sheets

A new type of intelligent composite structure is proposed, consisting of reinforced concrete and prestressed hybrid fiber-reinforced polymer sheets. The hybrid fiber-reinforced polymer consists of basalt and carbon fibers. The carbon fibers function as both sensitive and structural materials to improve stiffness of the hybrid fiber-reinforced polymer sheets and provide a self-monitoring function, whereas basalt fibers function only as structural materials to improve their ductility and decrease the cost. A series of experiments were performed to study the mechanical and monitoring performances of the hybrid fiber-reinforced polymer-concrete composite structures. The results show that their mechanical and self-monitoring performances are markedly upgraded through prestressing the hybrid fiber-reinforced polymer sheets. The prestress improves both the strengthening and monitoring performances. Compared with the control beams, the cracking, steel yielding, and peak loads are improved by 44%, 26%, and 36%, respectively. Results reveal that the prestress also upgrades the monitoring sensitivity and stability of the hybrid fiber-reinforced polymer sheets. Since the electrical behavior is closely related to the mechanical behavior of the hybrid fiber-reinforced polymer-concrete composite beams, the strain, cracking, steel yielding, and the debonding and rupture of the hybrid fiber-reinforced polymer sheets can be well identified through the resistance measurement. A built-in health monitoring function is, thus, demonstrated for the intelligent hybrid fiber-reinforced polymer-concrete composite structures.