SPH Simulation For The Injection Molding Flow Of Automotive Fiber Reinforced Composites

Due to the problems of environmental pollution and shortage of energy,automobile lightweight is an inevitable trend of the development of automobile industry.The application of lightweight materials is one of the main approaches to achieve lightweight of automobile,and plastic and its composites are promising lightweight materials with increasing application amount.Injection molding is the main fabricating process of plastic and its composites,and the filling flow is an important stage of the injection molding which partly determines the quality of the products.Therefore,it is necessary to investigate the injection molding flow of the plastic and its composites.Numerical simulation is an efficient method to study the injection molding flow,which can save the time and cost.Smoothed particle hydrodynamics(SPH)is a Lagrangian meshless particle method,and it has been successfully applied to the molding simulation.However,to our best knowledge,there is few application of the SPH in the injection molding,and has no work on the application of SPH to injection molding of fiber reinforced composites.Therefore,this dissertation investigated the SPH modeling and simulation of the injection molding flow of lightweight plastic and its composites.Firstly,this dissertation analyzed the basic theory and related numerical questions of SPH,including the principle of particle approximation,the deducing and SPH approximation of the conservation equations,the method to settle the instability of SPH,the implementation of boundary conditions,and so on.According to the above theories,the solution code of the SPH was constructed,and the Poiseuille flow and Couette flow were solved for verifying the stability and accuracy of the SPH method and code.Secondly,the SPH modeling of the injection molding flow was investigated,including the arrangement of boundary particles,the choice of viscosity model,and the value of initial particle distance.The SPH simulation of injection molding flow was performed,and the results were compared with those of VOF simulation,which showed that the simulation results of SPH and VOF about the resin flow agreed well.It demonstrated that the model of the injection molding flow was constructed reasonable,and the SPH method and code are feasible and accurate in simulating injection molding flow.Thirdly,the 3D SPH simulation for injection molding flow of the plastic wasresearched,and the results were verified by VOF simulation and experimental results.Then,the injection molding flow of three typical cavities was modeled and simulated using SPH method,and the resin flow in the cavities was studied.Additionally,the motion of the single fiber in the simple shear flow was simulated using SPH method,and the results were compared with the theoretical solution,which validated the accuracy of SPH method and code in simulating fiber motion.After that,the 2D and 3D injection molding flow of short fiber reinforced resin composite was modeled and simulated using SPH method,and the flow behavior of the resin melt and the orientation of the fibers were investigated,and the effects of the typical factors on the fiber orientation were studied.The results indicated that the stable U type fountain flow front was formed in the simulation;the fiber distribution in the cavity was not uniform,and the fibers were accumulated at some points in the cavity;the fibers aligned with the flow direction in the skin layer and inclined to the flow direction in the core layer,which was consistent with the experimental results.The orientation factor was used to evaluate the fiber orientation in the SPH simulation,the results showed that the orientation factor increases with the increase of fiber aspect ratio,while decreases with the increasing fiber content.Lastly,by comparing the results of the SPH and VOF simulation for micro-scale flow within the fiber tow,the feasibility of the SPH to simulate the flow in porous media was demonstrated.Then,the flow in the dual-scale continuous fiber preform during resin transfer molding was modeled and simulated using SPH method,and the effects of typical factors on the flow were also studied.The results indicated that dual-scale flow front was formed which lead to the formation of the void;void size increases with the increase of vertical inter-tow dimension while decreases with the increasing resin velocity and viscosity.