Experimental study on fatigue behavior of CFRP bars

The fatigue test of CFRP bars was carried out at the different cyclic stress, choose the 70% ultimate tensile stress of CFRP bar as the maximum cyclic stress, under the cyclic ratios of R=0.5 (the minimum-to-maximum stress ratio) and R=0 and the fatigue behavior of CFRP bars was investigated. The results showed the maximum cyclic stress of CFRP bar should be under 70 percent of ultimate tensile stress; when the maximum cyclic stress decrease 5 percent of ultimate tensile stress, the fatigue life of CFRP bars increase generally 10 times; with the decrease of cyclic ratios, the fatigue life of CFRP bars decrease heavily; for the brittleness, CFRP bar should possess a higher reserve of strength, the margin of safety against failure is a necessity; according to experimental cyclic stress-fatigue life curve, the fatigue behavior of CFRP bar is much better than the fatigue behavior of Q235 steel.