Numerical Simulation And Experimental Study On Resin Filling Process In VARTM

VARTM is a novel liquid molding technology in composites manufacturing which solves many problems in traditional molding process such as high cost,high energy consumption,high pollution or other issues.Therefore,it's widely used in plant fiber composites manufacturing which can make full use of the characteristics of light-weight,low-price,and easily available about plant fiber.Now it becomes a hot spot in plant fiber composites application fields.There are many factors which will influence the VARTM process.In this research,resin viscosity,vacuum degree,location of resin injection and output were selected to study their influence on the filling process.In this study,the molding parameters were optimized,so the filling time can be reduced and the production efficiency is improved.The jute fiber was selected as reinforcement in this research.According to the change of contact angle to analyze the resin infiltration on the jute fiber.The results showed that the contact angle become smaller after alkali treatment,and the infiltration character of capillary fiber also become better than that of untreated.Good wettability is a prerequisite for resin penetration,so based on Darcy's law,one-dimensional and two-dimensional permeability testing models were established to calculate the permeability of jute fiber under constant pressure injection.The permeability can be as basic parameters for simulation of resin filling process.Due to the plant fiber has the porous properties,the problem of resin flowing in the jute fiber can be treated as the in-compressible fluid filling in porous media.Therefore,a finite element model was established based Darcy's law and basic equations of fluid motion.The resin viscosity,vacuum degree,location of resin injection and output were selected as control parameters to study the problem of filling process by using PAM-RTM software.The result showed that with the increase of the viscosity,the filling time will become longer and the shape of flow front is consistent in variation.Although with the increase of the vacuum degree,the filling time decreases.In general,the filling time of the central point injection is shorter than the boundary injection,and the filling time is shortest under the mode of central point injection and boundary output.To compare with the simulation results,an experiment about the effects of resin viscosity,vacuum degree,resin injection and output mode on the resin filling process were investigated.The resin filling state at different time and filling time difference rate were analyzed to verify the result between simulation and the experiment.The result showed that it has a highly coincidence,and the optimized parameters also be acquired.The jute fiber laminates with different ply orientation angles were prepared by using the optimized parameters.From the macroscopic mechanical properties and the micro-structure of the section,the effect of the resin filling process on the quality of the laminate was analyzed.The results showed that different ply orientation angle has a diversion effect on the resin flow,in which the main defects in the molding process are resin enrichment,internal dry area,bubble residue.By taking the appropriate measures such as reduce the resin viscosity,increase the vacuum,improve the filling temperature and the ply orientation to optimize the resin filling process,and reduce the incidence of forming defects.