Study On Injection Parameter Optimization And Defect Prediction In Resin Transfer Molding Filling Process

Resin Transfer Moulding is a composite material moulding technology in which Resin is filled into the preformed fiber body and solidified under certain conditions.Because of its low cost,good operating environment,suitable for large structural parts of the integral molding and other advantages,the technology has a very broad application prospects in aerospace,automobile manufacturing,railway systems and ships.However,in the process of RTM filling,due to the numerous parameters affecting the resin infiltration fiber process,once the control is improper,the molded parts are prone to dry spots,bubbles and other molding defects.In order to select the appropriate process parameters and control the defects in the process of mold filling,the paper analyzes the flow behavior of resin in RTM process,set up a mathematical model of gas liquid two phase flow based on the model to optimize the RTM process parameters in the process of porous injection,and also on the formation of a dry spot bubbles and control carried on the thorough analysis.The specific research work of this paper is as follows:(1)The flow process of the resin in the fiber preform was analyzed.Based on the Darcy's law and mass conservation equation and combining the Navier-Stokes equations,established a RTM mold filling process gas liquid two phase flow model,and then the VOF method is used to track resin flow front,at the same time,combining with the PLIC reconstruction method to construct two phase interface,finally realized the simulation of RTM filling mold process accurately.In order to prove the correctness of the above numerical simulation method,the one-dimensional and two-dimensional filling flow experiments of the plate model were compared with the simulation results,and it was found that the resin flow front of the two models at any time was basically consistent,thus proving the correctness of the mathematical simulation method in this paper.(2)Based on the simulation of RTM filling process,the formation mechanism and control method of dry spots and bubble defects were analyzed.First expounds the formation and evolution mechanism of dry patches,edge effect is simulated the forming process of dry patches,and study when the fiber preform permeability heterogeneous body,the size of the partial penetration to the influence of the resin flow and the impact on the mold filling time,found that when local permeability small to certain degree form dry patches,mold filling time also increased sharply.Secondly,the formation mechanism of bubbles was analyzed,the relationship between the content of macroscopic and microscopic bubbles and the flow rate of resin was obtained,and a mathematical model was established to predict the content of bubbles.(3)In order to improve the production efficiency of large or complex structural parts formed by RTM,multiple injection ports are often used for simultaneous injection to improve the efficiency.This chapter to light helicopter landing gear as the research object,the combination of structure of porous RTM injection process parameters are optimized in the design,combining with the existing research proposed a evaluation scheme rationality of injection port and vent process performance index,and by using the index of seven groups of different injection scheme of the simulation results of the simulation after evaluation,get the optimal injection port and vent.Then,on the basis of the optimal scheme,the effects of injection pressure and injection mode on the resin flow were further studied,and finally,a constant flow followed by constant pressure injection curve was obtained as the injection scheme.