| Bisphenol A epoxy resin(DGEBA)has been widely used in aerospace,military,sports equipment and other fields.However,the high crosslinking network structure formed by DGEBA resin after curing makes the curing material brittle and has poor toughness,so it needs to be toughened.At present,the toughening method is physical toughening:toughening phase does not react with epoxy resin components,but only physical mixing and dispersion.Because these toughening phases improve the viscosity of epoxy resin system,it also involves the dispersion,size and interface compatibility of toughening phase,which brings inconvenience to the manufacturing process of the materials,and also affects the comprehensive properties of epoxy resin.In this work,the chemical toughening method is used:the toughener has active functional groups which react with epoxy resin.DGEBA resin was modified with isocyanate(MDI),and an epoxy resin toughener with oxazolidone(OX)structure was synthesized.The toughener has active functional groups and can participate in the reaction of epoxy resin system.The comprehensive effect of the toughener on DGEBA resin matrix was evaluated,and its effect on the properties of high strength T1100 carbon fiber reinforced composites was investigated.It is a bicycle component made of T1100 carbon fiber:1.Using DGEBA resin and MDI as the main raw materials,the bulk polymerization method is used to synthesize materials containing OX structure.The synthesized product was tested and analyzed by infrared spectroscopy and DSC,and it was determined that the reaction conditions were:2-MI as a catalyst,the reaction temperature was controlled at 120?,and the molar ratio of reactive groups was E/I of 3:1;2.The synthetic OX material is used as a toughening agent to modify the DGEBA resin so that its Tg and initial thermal decomposition temperature are increased to 173? and 355?,respectively.And the impact strength,bending strength and modulus are increased by 83%,30%and 12%respectively;3.T700,T800 and T1100 carbon fiber composite prepreg were prepared by hot melt method with modified epoxy resin as matrix resin,and carbon fiber reinforced polymer matrix(CFRP)composite laminates were prepared by molding process.After toughening,the flexural strength and modulus of the T1100 carbon fiber composite laminate reached 2000 MPa and 175 GPa,and the impact strength reached 260 kJ/m2.Compared with the CFRP composite laminate without oxazolidinone material,they were improved 26%,8.4%and 24%;And the compression strength(CAI)of the composites after impact is increased from 244 MPa to 275 MPa,indicating that the modified resin can give full play to the high performance advantages of T1100 carbon fiber.ABAQUS finite element method is used to simulate the three-point bending process of composite materials,and the stress situation in the bending process is analyzed.The laminated plates after impact are scanned and analyzed by ultrasonic C-scan.It is found that the failure mode of the laminated plates before and after toughening has changed,and the principle of its generation is analyzed theoretically;4.Using T1100 carbon fiber and resin system containing OX polymer as materials,bicycle parts(frame and front fork)were prepared,and their comprehensive mechanical properties were evaluated.The test results show that the performance of the modified epoxy resin CFRP Composite bicycle parts is improved:the fatigue resistance of the frame is improved,after 50000 cycles of fatigue test,the frame is not damaged,and the maximum load of the head tube can reach 7661.5 N;at the same time,the bending resistance of the front fork is 250.4 Kg,and the impact resistance is also improved. |
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