Experimental study on high-temperature relaxation behavior of carbon fiber reinforced polymer cable

Abstract

In order to fully investigate the relaxation behavior of carbon fiber reinforced polymer (CFRP) cable exposed to high temperature, both steady state-constant displacement and temperature (ST-CDT), and transient state-constant displacement and temperature (TR-CDT) tests were conducted on specimens. The failure modes, stress loss laws and rupture times of high-temperature relaxation specimens were determined under ST-CDT and TR-CDT conditions. After high-temperature relaxation tests, high-temperature tensile tests were conducted on samples without rupture to obtain its residual mechanical properties. Final stress losses and stress loss rates of CFRP cable specimens determined by ST-CDT tests were compared with these of TR-CDT tests to clarify the effect of temperature-load path. A high-temperature relaxation model was developed to characterize the variation law of stress losses for CFRP cables under ST-CDT and TR-CDT conditions. A correlational model between stress loss and creep strain rates in steady stages of CFRP cables under high temperature was calibrated. The obtained results demonstrated that high-temperature stress losses of CFRP cables were closely correlated with target temperature, initial stress level and relaxation duration. The application of initial pre-tension load before heating accelerated the stress loss rate in transition relaxation stage and final stress loss of CFRP cable under high temperature.