Analyzing and investigating the effects of high temperatures on the performance of carbon fiber reinforced polymer (CFRP) composite cables

Carbon fiber reinforced polymer (CFRP) cables are lightweight and have high strength,fatigue resistance, corrosion resistance, and high seismic performance. Carbon fibermaterials are widely used to strengthen buildings and bridges. In bridges with a cablesupport system, CFRP cables can be substituted for steel cables, thus reducing the weightof the bridges, decreasing the scale of the substructure, and allowing increased bridgespan, reducing the overall bridge cost and the technical challenges of construction .However, CFRP cables increase fire risk during construction and operation. The tendons in CFRP cables are composed of carbon fiber precursors and resin matrixes. The resin matrixessoften when exposed to high temperatures due to weak high temperature resistance,resulting in rapid decay and degradation of the overall mechanical performance of thetendons at high temperatures, endangering the overall safety of the bridge structure. In mechanical engineering, when a CFRP-reinforced structure is subjected to fire, both the structure and CFRP are simultaneously affected by elevated temperature and mechanical loading. In the Eurocodes, the strengths of concrete and steel are described to be reduced with increased temperature; however, the codes do not describe the performance of hand-laid CFRP. This paper presents the thermomechanical performance of hand-laid CFRP with and without thermal insulation under different mechanical loading conditions. Experimental tests were conducted to identify the maximum transient heating temperature and duration to which CFRP can be exposed at different levels of mechanical load. The results show that when the applied load increases, the rupture temperature and maximum exposure duration decrease. At ۲۰ °C, the rupture temperature of CFRP gradually decreases when the applied load increases from ۱۰% to ۵۰% of the material's ultimate strength; at room temperature, as the applied load reaches ۷۵% of the ultimate strength, the rupture temperature significantly decreases. Likewise, the exposure duration gradually decreases when the applied load varies from ۱۰% to ۵۰% of CFRP's ultimate strength, and decreases considerably when the applied load is ۷۵% of the ultimate strength. Additional tests were conducted on CFRP protected by an insulation material to characterize the effectiveness of the used insulation material used on the performance of hand-laid CFRP subjected to thermal and mechanical loading. Finite element models were used to investigate the thermal conduction, and these models were successfully validated by the experimental results. Thus, the models were confirmed to predict the fire protection capability of the used insulation material reliably and accurately.

Keywords:

Carbon fibre reinforced polymer (CFRP) , Elevated temperature , Thermo-mechanical behaviour , Fire protective system