Interface Modifications Of Carbon Fiber Reinforced Resin Composite And Study Of VARI Process Of Glass Fiber Reinforced Resin Composite

Carbon fiber/resin composites has many advantages.Carbon fiber and carbon fiber/resin composites replace metal materials in engineering due to their advantages of low density,high strength,high impact toughness,high corrosion resistance and high chemical stability.However,the surface of carbon fiber is smooth,the chemical inertia of surface is large,the surface energy is low.All of these make it difficult to bind fiber with resin effectively,which will reduce the mechanical properties of the composite.Besides,vacuum assisted resin injection molding(VARI)is usually used to prepare high-performance fiber composite materials.But its process parameters are obtained by trial and error method,which is high cost and low efficiency.Therefore,improving the interface performance of fiber/matrix and the accuracy of process parameters are the key points to promote the development of fiber composite industry.In this paper,the interface modification of carbon fiber resin matrix composites and the simulation of VARI process parameters were studied,and the following three aspects were carried out:1.Ethylenediamine(EDA)with flexible structure and p-phenylenediamine(PPD)with rigid structure were selected as grafting reagents.The surface of carbon fiber was modified by chemical grafting of diamines.Through TG,FTIR,XPS,DCA and SEM tests.At the same time,it was also found that the surface energy of fiber grafted by EDA was increased greatly,and the surface roughness of fiber grafted by PPD was increased greatly.The composite of carbon fiber grafted both EDA and PPD had the highest short beam shear strength,which was 44.9%higher than that of untreated carbon fiber.2.Simulation of VARI:firstly,the pressure distribution model of resin filling process was established according to Darcy’s law.Secondly,a series of process parameters,such as permeability,porosity,resin viscosity and injection pressure,were obtained by experimental measurement and calculation.The parameters were imported into PAM-RTM software to simulate 18 cases,which were divided into 7 control groups according to the different parameters.The simulation results show that:the different injection mode,vacuum port setting,laying mode and laying angle will affect the morphology of resin flow front;The permeability of fiber and the number of injection ports are the main factors that determine the flow rate of resin front,and large permeability and multiple injection ports can effectively improve the filling efficiency;If there are two orthogonal pressure gradients in the filling process,it is not conducive for resin flowing.3.According to the simulation results,16 groups of VARI processes were set up according to the simulation scheme,and the resin flowing situation during simulation and actual process was compared.After that,the composite produced by VARI were tested in bending and short beam shear.According to the different parameters,six control groups were set up for the mechanical properties test.The experimental results showed that:the orthogonal pressure gradient can improve the bending performance of the composite;The bending performance of the normal stress along the fiber surface direction is much higher than that of the normal stress along the vertical fiber surface direction;The plain weave fabric has more corrugated structure than the twill weave fabric,which will reduce the mechanical properties.But its binding capacity with the resin matrix is higher than that of the twill woven cloth,so the shear strength of the short beam of plain weave fabric is better;The permeability,the number and location of the vacuum port have no significant influence on the shear strength of the short beam,but the post curing treatment can effectively improve the shear strength of the short beam and improve the interface performance.