| The anti-corrosion and reinforcement of metal pipes have always been the focus of attention in the field of composite materials.Photo-curing prepregs were considered ideal for reinforcing metal pipes because of their suitable outdoor construction conditions.However,it was difficult to prepare prepregs by hot-melt two-step method for low-viscosity photocurable resin.At the same time,the reinforcement effect of composites on metal pipes could be predicted and verified by finite element analysis.Therefore,a photo/thermal synergistic curing epoxy resin system was designed to improve the film-forming properties and low temperature curing activity.In addition,the finite element software was used to analyze the composite reinforced metal pipe.The effective verification of the reinforcement effect of composite on the metal pipe under internal pressure was realized and the damage failure mechanism of the composite single-layer plate was proposed.(1)Based on cycloaliphatic epoxide(ECC)and bisphenol F epoxide(DGEBF)as matrix,acrylate(TPGDA)as a diluent,two kinds of free-radical/cationic photo/thermal synergistic curing resins EC/TP and DG/TP were designed.The film forming process and curing kinetics of the resin system were studied.The influence of photo pre-curing time on the viscosity and curing degree of the resin systems was analyzed by DSC,and the pre-cured resins were used to prepare resin films at room temperature and to impregnate fibers at low temperatures.The initial curing temperature of the resin systems at 70℃ was determined by non-isothermal DSC,and the isothermal curing prediction curve was obtained by the Vyazovkin integral method.Based on the above results,it was determined that the thermal curing process of the EC/TP system was 70℃/8 h,and the thermal curing process of DG/TP system was 70℃/17 h.The fabric prepreg was prepared by impregnating E-glass fiber with EC/TP resin system,and the mechanical strength and elastic constant of the composite laminates were obtained by testing.(2)The EC/TP fabric composite was used to reinforce the metal pipe,and the finite element model was established by ABAQUS software,and the mechanical parameters were input into the model.The reinforcement effect of metal pipe under internal pressure loading was evaluated,and the damage failure mechanism of composite was proposed by finite element analysis.According to the stress analysis,it was determined that the yielding and the bursting failure of the metal pipe occurred under the internal pressure of 13.9MPa and 20.0 MPa,respectively.However,the bursting failure internal pressure of the composite reinforced metal pipe was 24.0 MPa,which was increased to 120% of the unreinforced pipe.According to the failure criterion of composite,the tensile damage of hoop fibers occurred when the internal pressure was 22.8 MPa.According to the stiffness degradation analysis of composite,it was pointed out that the stiffness of the composite continued to degrade under the accumulation of fibers damage,and when the internal pressure was 24.0 MPa,a large area of the fibers were broken,resulting in catastrophic failure of the composite structure and the loss of reinforcement ability. |
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