Fatigue Performances Of Pultruded Carbon Fiber Reinforced Polyurethane Composite Plates

Carbon fiber reinforced polymer composites(CFRP)is a kind of polymer with excellent mechanical properties,corrosion resistance,light weight and high specific strength,so it has great application potential in civil engineering field.Polyurethane(PU)is a kind of polymer resin with high strength,high toughness,high durability and high adhesion,which is a good material for CFRP matrix.However,PU based CFRP materials are rarely used in civil engineering.It is urgent to study the fatigue properties of polyurethane based CFRP materials.In this paper,the bending fatigue properties of pultruded PU based CFRP and the effects of immersing in water,seawater and alkaline solution environment on the bending fatigue properties were studied by accelerating aging at high temperature.Firstly,the bending fatigue properties of CFRP plate under different strain levels were studied,the strain fatigue life curve was obtained,and the stiffness degradation model and the fatigue life prediction model based on Weibull distribution were established.The results show that the CFRP plate has good bending fatigue resistance,such as fatigue life of more than 10~5 times at 1.8%strain level.Under 85%confidence level,CFRP plate has 82402 and 11221 times fatigue life at 1.8%and 1.9%strain.Secondly,the bending fatigue properties of CFRP Plates under 1.8%strain after accelerated aging in distilled water,seawater and alkaline solution at high temperature(60?)were studied.The fatigue life curves of the plate under different immersing time were obtained,and the fatigue life prediction model based on Weibull distribution was established.The results show that:the bending fatigue life of the CFRP plates decreases with the increase of aging time after immersing in water,seawater and alkaline environment for 7,15 and 30 days;the decreasing rate of life of the samples immersed in water environment decreases,while that of the samples immersed in seawater and alkaline environment increases.It is speculated that the post curing effect of PU matrix in seawater and alkaline environment is inhibited.