Prediction Of Warpage Behavior Of Thermoplastic PMC Laminated Structure

PMC(Polymer Matrix Composites)is a polymer-based composite material.Thermoplastic PMC is a material composed of a thermoplastic resin matrix and a fiber-reinforced phase,which is a fiber-reinforced thermoplastic composite material.Fiber-reinforced thermoplastic composite material is a new type of composite material,which has the advantages of high specific strength,high specific rigidity,good impact damage resistance,and slow damage expansion.Therefore,it is widely used in military,aerospace and other fields.At present,in order to pursue multi-mechanical properties,it has become a new research hotspot to combine a variety of different properties of resin matrices and fiber reinforcements to obtain a composite structure with a laminated structure.After reading a large amount of domestic and foreign literature,it is found that researchers have rarely studied the injection molding methods of fiber-reinforced thermoplastic composites,and there are very few studies on the molding methods of their laminated structures.Therefore,this thesis will be based on the finite element software Moldflow to simulate the injection molding process of the thermoplastic PMC laminated structure,adopt solutions of optimizing the packing process,optimizing the process parameters,sequential injection molding,and different molding technologies to improve the amount of warpage and deformation,and further explore the influence of different optimization methods on its warpage deformation.In order to compare the effects of different molding methods on the warpage of the thermoplastic PMC laminated structure,the simulation process of the secondary molding and the overmolding is carried out by using the same mesh division,material combination,gate position and quantity,process parameters and runner system through Moldflow software.According to the comparative analysis of simulation results,it is found that the two injection filling environments are different in the two injection molding processes,leading to the inconsistent flow behavior of the melt in the two injection molding processes,and further changing the pressure distribution and volume shrinkage distribution,resulting in the difference of warpage deformation;According to the warpage deformation results of the two moldings,it is concluded that the overmolding can better ensure the molding quality of the thermoplastic PMC laminated structure.Based on the analysis of the results of initial overmolding,it is found that themain causes of warpage of the thermoplastic PMC laminated structure are excessive temperature difference at the flow front,insufficient packing process and orientation effect;In order to further optimize the warpage,the scheme of optimizing the packing time and packing pressure is adopted to improve insufficient packing process to optimize warpage caused by uneven shrinkage;The mold surface temperature,melt temperature and injection time of the first and second injection were optimized by orthogonal test to reduce the temperature difference at the flow front,so as to improve the warpage caused by uneven shrinkage;The method of adopting the sequential injection from the center to the outside is to improve the warpage caused by orientation.By analyzing and comparing the results of the above schemes,it is concluded that the amount of warpage caused by uneven shrinkage was reduced from0.72 mm to 0.36 mm in the original scheme,which is optimized by nearly 50%;The amount of warpage caused by the orientation effect is reduced from 0.095 mm to0.069 mm,which is optimized by about 27%.The computer simulation of the thermoplastic PMC laminated structure can find a processing technology that saves costs and improves molding efficiency for actual processing,and also provides numerical preparation and methodological references for research in related fields.