Study On Injection Molding Optimization Of Process Parameters And Macro-Mesoscopic Simulation And Experimental Of Composite Materials

Short fiber composites are composites with polymer as matrix phase and various short fibers as reinforcing phase.They have the advantages of high specific strength,corrosion resistance,fatigue resistance and good workability.Therefore,they are widely used in aerospace,aviation,household appliances,electronics and other fields.Injection moulding is one of the main moulding methods of short fiber composites,which has the advantages of simple processing and low cost.However,in the process of forming,it is easy to cause the size error of the parts due to shrinkage deformation.Although the research and design of injection parts will be based on the characteristics of the structure and process of injection parts,the shrinkage results of injection parts are often different with different materials and different process parameters,so it is usually difficult to predict accurately.At the same time,the prediction of mechanical properties of injection moulded products for load-bearing structures is also very important.Therefore,how to predict and improve the quality and mechanical properties of injection parts in the design stage has become an important research topic.Firstly,the injection part model was established by three-dimensional drawing software CATIA.Moldflow software was imported to diagnose and repair the model,and mesh was divided at the same time.The forming material was selected and the gate position was set.Then the preliminary injection molding simulation was carried out,and the simulation results under the default parameters were obtained.Based on the volume shrinkage,shrinkage depth and warpage deformation of the parts,six factors and five levels orthogonal experiments were established and simulated by Moldflow software.By calculating the signal-to-noise ratio(SNR)of the simulation results and analyzing its mean and range,the optimum combination of injection molding process parameters and the influence of process parameters on each index were obtained.Finally,based on the comprehensive evaluation of weighted comprehensive scoring method and taking the comprehensive quality of injection parts as the index,the process parameters of injection moulding were optimized.The results showed that compared with the simulation results under default process parameters,the maximum volume shrinkage rate of injection moulding was reduced by 48.37%,the maximum shrinkage depth was reduced by 55.56%,and the maximum warpage deformation was reduced by 12.74%were optimized.Secondly,the part model is cut into several regions in ABAQUS software.The fiber orientation tensor of each region of the part can be obtained by the result of Moldflow injection molding.The average fiber orientation tensor of each region can beobtained by selecting a number of points and extracting the data of fiber orientation tensor in each region and calculating the average value.The average fiber orientation tensor of each region is taken as a parameter,and the parameters of fiber and matrix are set up.The corresponding RVE model is established and the engineering elastic constants and stiffness matrices are calculated.The results were imported into ABAQUS software,and the mechanical properties of the injection-moulded component were obtained by simulation.Finally,according to the completed simulation,the injection moulding test parts were prepared on the injection moulding machine.Before injection molding,glass fibers with 6 mm length and 20% volume fraction were evenly mixed with PA6 resin,and various technological parameters were set up.Under the optimum technological parameters,the injection molding test pieces were obtained.Firstly,the overall dimensions of the test pieces were measured,and then the whole compression test was carried out on the universal testing machine to test the mechanical properties of the whole part and the gate of the injection moulding test pieces.The results show that the overall dimension error between the test part and the simulation part is small,and the mechanical properties of the test part are close to the simulation results,which verify the accuracy of the simulation results.