VARTM Process And Interfacial Modification Of Bamboo Fiber/Epoxy Composite

Bamboo fiber/epoxy composites have the advantages of light weight and high strength,good fatigue resistance and good cushioning properties,and they also have excellent characteristics such as low cost,low energy consumption,and environmental protection.However,in the field of RTM(vacuum assisted resin transfer molding)process,due to the limitations of the plant fiber itself and the characteristics of the RTM process,there are disadvantages such as unstable performance,difficult control of the injection process,poor resin and fiber impregnation,and poor interface performance.In this study,bamboo fiber(BF)was used as the reinforcement,and epoxy resin(EP)was used as the matrix resin system.The bamboo fiber/epoxy composite material(BF/EP)was prepared by the RTMprocess.The influence of interfacial wetting properties between matrix epoxy resin and process parameters such as fiber content,injection pressure,molding temperature,and vacuum degree on the mechanical properties,die time and porosity of materials.At the same time,the coupling agent(KH550)and wetting agent(Biker 358N)were used to modify the interface,and the effect of coupling agent and wetting agent on the mechanical strength and thermodynamic properties of the modified composite was explored to reveal its interface.Compatibility enhancement mechanism.The purpose is to optimize the RTM molding process parameters,explore the optimal process scheme in the test range,and at the same time improve the physical interface properties through modification to improve its physical properties,providing a theoretical basis and data support for the development and utilization of bamboo fiber/epoxy composite.The main research contents and results are as follows:(1)The wettability of epoxy resin E-51 system to bamboo fiber was investigated from two aspects:the surface free energy of bamboo fiber and the dynamic contact angle between bamboo fiber and epoxy resin system.The results show that the dispersion component,polar component,and surface free energy of bamboo fiber are calculated to be 27.25 mN/m,15.05 mN/m,and 42.30 mN/m,respectively;while the surface tension of the epoxy resin system is 41.30 mN/m,After modification by the coupling agent/wetting agent,the surface tension of the epoxy resin system further decreased.When the mass fraction of the wetting agent was 2 wt%,the surface tension of the epoxy resin reached a minimum value of 31.33 mN/m;The surface free energy of the fiber.Therefore,judging from the perspective of thermodynamics,the epoxy resin system used in this experiment can spontaneously wet bamboo fibers.The dynamic contact angle between the bamboo fiber and the epoxy resin system is 76.63°,and the dynamic contact angle between the two is less than 90°,which indicates that the epoxy resin system used in this experiment can wet the bamboo fiber..(2)Bamboo fiber/epoxy resin composites were prepared using the RTM molding process.The RTM process parameters such as fiber content,injection pressure,molding temperature,and vacuum were used to investigate the mechanical properties,porosity,and die time of the RTM process.Impact.The research results are as follows:Bamboo fiber reinforcement can effectively enhance the mechanical properties of bamboo fiber/epoxy resin composites,and as the fiber content increases within a certain range,the mechanical properties of the composites are improved.However,after the bamboo fiber reached a certain proportion in the matrix(40%),the continuous increase of the fiber content actually reduced the mechanical properties of the composite.When the fiber content is 40wt%,the tensile strength and impact strength of the composite material reach the best,which are 52.74 MPa and 131.41 J/m,respectively.In summary,within the scope of this study,when the fiber content is 40wt%,the comprehensive mechanical properties of bamboo fiber/epoxy resin composites are the best.TG and DSC tests show that with the increase of the fiber content,the endothermic peak of the composite material advances,and the temperature at which the endothermic peak is reached also gradually rises,which indicates that the addition of bamboo fibers reduces the temperature at which the polymer reaches the same melting degree Reduced polymer melting time.RTM process parameter experiments show that during the RTM process,the molding temperature has the most significant effect on the properties of the composite.When the fiber content is 40 wt%,the molding temperature is 120?,the injection pressure is 0.5 MPa,and the vacuum is-0.07 MPa,the bamboo The tensile strength of the fiber/epoxy composite is the best,which is 52.74MPa;the increase of the injection pressure will lead to a decrease in the die time,but with the continuous increase of the injection pressure,the decrease of the die time appears to be gentle.The trend is that when the injection pressure is 0.9 MPa,the die reaches a minimum value of 62s;increasing the vacuum can effectively reduce the porosity of the bamboo fiber/epoxy composite.When the degree of vacuum is-0.07MPa,the porosity reaches the lowest value of 1.327%.(3)Modification of bamboo fiber/epoxy resin composites using coupling agents/wetting agents.The effects of different types and different amounts of modifiers on the mechanical properties and dynamic thermodynamic properties of composite materials were mainly studied.The study found that the mechanical properties of BF/EP composites,such as tensile,flexural,and impact resistance,were significantly improved after the epoxy resin was modified with a coupling agent/wetting agent.Among them,the modification of the coupling agent improved the mechanical properties more.Obvious effect.When the bamboo fiber content is 40%and the coupling agent mass fraction is 3 wt%,the mechanical properties of the composite material are optimal,and the tensile strength,bending strength,and impact strength are 74.76 MPa,91.76 MPa,and 214.92 J/m;The storage modulus of the composite modified by the coupling agent increases and the loss modulus decreases;after the modification of the wetting agent,the loss modulus of the material is significantly lower than that of the coupling agent.Both modifications have improved the dynamic thermodynamic properties of the material;analysis by SEM and FTIR shows that both the coupling agent and the wetting agent can improve the interfacial compatibility between the resin and the fiber by improving the wettability of the resin.