Study Of Tensile Properties Of Carbon Fiber Composite After Coupled Temperature-moisture-load

Carbon fiber composites have been widely used in the field of building reinforcement because of their high modulus,high strength,high ratio and corrosion resistance.But the durability of carbon fiber/epoxy resin composites is less,especially high and low temperature and humidity coupling,high and low temperature Study on Durability after Circulating-Humidity-Load Coupling.These two coupling effects will lead to significant changes in the mechanical properties of carbon fiber composites.This will greatly affect the safety of reinforced buildings.Therefore,there is a need to investigate the mechanical properties of carbon fiber composites after temperature cycling-humidity coupling and temperature cycling-humidity-load coupling.This paper investigates the comparison of experimental results of epoxy T700 carbon fiber reinforced composites（EP-T700CFRP）subjected to different cycles of temperature-temperature cycling in the environment with and without water immersion,no-load and different loading conditions.The tensile properties of EP-T700 CFRP sheets under the coupling effect of temperature-temperature-cyclemoisture and temperature-temperature-cycle-moisture-load and the mechanism of interfacial damage were investigated by comparing the experimental results of different cycles of temperature-temperature cycling in the environment with and without water immersion,no load and different load conditions,and finally by data fitting methods for residual strength prediction model was calibrated,and the study resulted in the following The main conclusions of the study are as follows:（1）The tensile strength of epoxy resin-based carbon fiber reinforced composites showed a general trend of decreasing,then increasing and then decreasing with the increase of temperature cycles;the cracking was the most serious at 5 temperature cycles,and the tensile strength reached the lowest point.As the increase of cycle numbers to achieve 100,the tensile strength of material could achieve the peak value and then decreases.There is little effect on the tensile modulus.The microcracks at the interface between the resin matrix and the fiber have shown to be the main cause of the decreasing of composites strength.The coupling effect of humidity promotes the expansion of cracks and significantly weakens the tensile properties of the resin-based carbon fiber composite.（2）The test results show that the coupling of temperature cycle-humidity-load has a greater impact on the durability of epoxy resin-based carbon fiber reinforced composites,and the increase in the temperature cycle of tensile strength shows an overall trend of first decreasing,then increasing and then decreasing.however,there are significant differences in the time periods when peak and trough values occur.Humidity and load level have little effect on the tensile modulus of EP-CFRP.The material may have experienced post-curing effects that enhanced the interfacial bonding while leading to an increase in the tensile strength of EP-CFRP.Microcracking at the resin matrix-fiber interface was shown to be the main cause of the late strength loss of the composite;at the same time,the coupling effect of moisture and load promoted the crack extension and intensified the damage of EPCFRP.The microcracks generated at the interface between the resin matrix and the fiber have been proved to be the main reason for the strength reduction at later stage.The coupling effect of humidity and load promotes the expansion of cracks and exacerbates the damage to EP-CFRP.（3）Based on the results of the two-factor coupling of temperature cycling-humidity and the three-factor coupling of temperature cycling-humidity-load,the damage analysis was carried out,and finally a nonlinear fitting method was used to give the damage model of EP-CFRP after the three-factor coupling of temperature cycling-humidity-load.