Mechanical Properties Of FRP-block Under Coupling Effect Of Freeze-thaw And High Temperature

In recent years,fiber reinforced polymer/plastic(FRP)has been widely used in masonry reinforcement due to its light weight,high strength and good durability.However,under the environment of alternating freezing and thawing and high temperature in the northern region,some problems will be exposed after long-term service of FRP masonry,such as the decline of bond strength and the deterioration of FRP materials,which will seriously affects the reinforcement effect of FRP masonry.Therefore,it is of great scientific significance to explore the mechanical characteristics of FRP-block interface under the coupling environment of freeze-thaw and high temperature.Therefore,from the mechanical properties of materials to the bonding interface between FRP and block,this paper systematically expounds the coupling effect of freezing and thawing and the influence of high temperature(60℃)environment and freezing and thawing environment on the mechanical properties of FRP-block.The specific research contents is as follows.(1)The mechanical properties of CFRP shale brick,CFRP clay brick,GFRP shale brick and GFRP clay brick under the coupling environment of freeze-thaw and high temperature are analyzed by finite element method,and the mechanical properties of FRP block are analyzed,and the effects of FRP types and brick types on interfacial peeling bearing capacity are discussed.(2)Based on the analysis results of FRP-block bonding interface,the degradation law of interface peeling bearing capacity with temperature and freeze-thaw is regressed,and the interface peeling bearing capacity model under the coupling action of freeze-thaw and high temperature is obtained by using the coupled damage evolution equation.(3)The mechanical properties of CFRP,shale brick,epoxy resin and CFRP shale brick under the coupling action of high temperature,freeze-thaw cycle and high temperature are studied experimentally,and the influence of three environments on the mechanical properties of FRP block is discussed.The main conclusion is as follows.a)After being placed in high temperature environment for 21×12h,the tensile strength of epoxy resin and CFRP decreased by 12.93% and 20.13% respectively,and the interface peeling ability of CFRP shale brick decreased by 26.28%.The compressive strength of shale brick changes within 10% at 60℃,which shows that the environment at 60℃ has little influence on compressive strength of shale brick.b)In the freeze-thaw environment,due to the influence of freeze-thaw cycle on the microcracks of the specimen,when the freeze-thaw cycle reach 30 times,the tensile strength of epoxy resin and CFRP,the compressive strength of shale brick and the interfacial peeling capacity of CFRP-shale brick decrease by 19.65%,34.37%,26.16% and 42.95% respectively.c)Under the coupling environment of freeze-thaw and high temperature,when the coupling cycle reaches three times,the tensile strength of epoxy resin and CFRP,the compressive strength of shale brick and the peeling bearing capacity of CFRP-shale brick decrease by 33.93%,44.38%,31.62% and 43.81%,respectively.By comparison,the order of damage caused by three environments to the peeling bearing capacity of FRP-block interface is as follows: coupled action of freeze-thaw and high temperature > freeze-thaw cycle > high temperature(60℃)environment.d)On the basis of parameter analysis,the effects of FRP type,brick type and interfacial bond length on interfacial peeling bearing capacity are analyzed.