Study On Fiber Concentration Distribution Of Injection Molding Products Of Short Fiber Reinforced Polymer

It is of great significance to study the fiber concentration distribution of short fiber reinforced thermoplastics composites which have been widely used in aerospace,biomedical fields etc.In this paper,a systematic study is carried out on fiber concentration distribution in injection molding process of short fiber reinforced polymer composites,which is based on Fluent software.The main research contents and conclusions are as follows:(1)Firstly,based on Fluent software,this paper has realized the simulation of two-dimensional filling flow process for short fiber reinforced polymer melt.The main work is that the author further develops a Cross-WLF viscosity model by using the Fluent UDF,and then realizes the numerical simulation of polymer melt filling flow which shows that considering the air phase and using the CLSVOF interface tracking method is more reasonable in Fluent,on this basis,the author analyzes the rule of fiber concentration distribution by using the DPM model and the DDPM model.The rectangular models with different aspect ratios and different mass fractions,the L-shaped corner model and the flow around cylinder model has been analyzed.The main rule is that fiber concentration distribution along the length and width directions is uneven and the distribution curve shows the “saw tooth” shaped wave which has a significant decrease of fiber concentration in the near wall,the uniformity of fiber concentration becomes higher and higher as the fiber aspect ratios and the fiber mass fraction increase,the uniformity of the fiber concentration in the zone 2 of the L-shaped corner decreases along the width direction,the symmetry of the fiber concentration in the zone 2 of the cylinder decreases along the width direction.(2)Secondly,the work is extended to three-dimensional simulation based on the two-dimensional simulation technology.The cuboid model considering gravity and different thickness has been analyzed.The main rule is that fiber concentration distribution along the thickness direction is also uneven and the fiber concentration distribution curve also shows the “saw tooth” shaped wave which has a significant decrease of fiber concentration in the near wall,furthermore,the uniformity of the fiber concentration distribution with gravity is slightly higher and there is a certain degree of asymmetry along the thickness direction,however,the curve widens to both sides increasingly with the increase of the thickness and the law of the concentration distribution in the thickness direction has a tendency to approach the law of the concentration distribution in the width direction.(3)Finally,this paper carries out simulation analysis on typical acutual injection molding products of the standard tensile specimen and the ring gasket.With the aid of micro focus X ray CT equipment,the local area of the products is scanned by 3D scanning,and then the experimental data has been processed by ImageJ software and MATLAB software.The experimental results and the numerical simulation results are compared and discussed,the conclusion shows that the numerical simulation results of fiber concentration distribution based on Fluent software is in good agreement with CT scan experimental results,which indicates that the simulation work has a certain rationality and it can provide some theoretical guidance and prediction for the fiber concentration distribution of typical acutual injection molding products.