Effect of hygrothermal and freeze-thaw cycles on mechanical properties of kiloton CFRP cable with self-monitoring function

Hygrothermal and freeze-thaw cycles are the key factors that lead to the performance degradation of carbon fiber reinforced polymer (CFRP) composite in bridge structures. A comprehensive investigation into the performance evolution of CFRP rods and large-scale CFRP cables under such cyclic conditions is imperative. In the present paper, the evolution of mechanical properties and glass transition temperature (T_g) of CFRP rod under 50 hygrothermal and freeze-thaw cycles was investigated. The verification data on the mechanical performance of full-scale kiloton CFRP cables post-exposure to these cycles was obtained. The optical frequency domain reflectometry (OFDR) strain monitoring was used to obtain the effect of hygrothermal and freeze-thaw damage on mechanical properties. The results showed that the mechanical performances of the CFRP rod had no significant degradation after hygrothermal and freeze-thaw cycles, while T_g of the CFRP rod decreased by 6.72 %. In addition, the maximum thermal strain and moisture strain of CFRP cable were 264 με and 38 με, respectively, indicating a negligible influence of hygrothermal and freeze-thaw damage on their mechanical properties. Furthermore, CFRP cables demonstrated the capability to withstand 50 cyclic loads (0.40–0.80 ultimate tensile loading) post-exposure, with a final residual tensile strength retention of 105 %. These findings provide key verification data for the durability design of CFRP cables in bridge structures.