Study On Chopped Carbon Fiber Reinforced Thermoplastic Polymer Molding Process

Thermoplastic composite materials,especially carbon fiber reinforced high performance thermoplastic composite materials are not widely used because of the high manufacturing cost and process is not yet perfect,which is caused by the expensive raw materials,complicated process and high consumption of process.Therefore,reducing the manufacturing cost of thermoplastic composite materials will remain a major research topic of science and technology workers.Rhometers,as the very important tools in the analysis of raw materials and formula processing performance,is getting better-known with its important role and will be used more and more widely.Based on the synthesis of various characterization methods,this thesis has established the method of determining the injection molding process parameters for the chopped carbon fiber reinforced thermoplastic composites.Pure nylon 66 and composite aggregate containing 10%and 20%carbon fiber as raw materials,it analyzed the basic features of the fiber reinforced composites with polarizing microscope,scanning electron microscopy(SEM),thermogravimetric analyzer and capillary rheometer.The experiment shows that softening point of three kind of aggregate increase,it’s 251℃,262℃ and 262℃ respectively;Initial decomposition temperature is increased with the increase of fiber content,it’s 304.6O℃,309.8℃ and 309.8℃ respectively,and the maximum decomposition temperature is 429.8 ℃ 433.5℃ and 433.5 ℃ respectively;Distribution for fiber draw ratio(L/D)is mainly 40～70;Great changes of the fiber orientation and distribution have taken place after flow forming.Using capillary rheometer and self-made mold,this thesis has made detailed flow analysis and the injection molding simulation for composite aggregate of different fibre content.The experiment mainly sturdyed the flow performance of thermoplastic resin after joining chopped carbon fibre,and got the viscosity-temperature,viscosity-shear rate and viscosity-shear stress curve,which makes it convenient to identify the injection molding process parameters of fiber reinforced resin.It can save a lot of materials,even less timesaving and laborsaving.Experiment shows that carbon fiber reinforced resin belongs to the power law fluid,and its viscosity changes greatly with temperature and pressure,which enter a stable region with proper temperature and pressure.The suitable molding temperature range of three kind of aggregate are 278～283℃(PA66),288～292℃(CF10%/PA66)and 292～298 ℃(CF20%/PA66);Though the capillary entry pressure correction to three kind of melt,we can get the Bagley correction factor is 4.3,4.5 and 5.1,and the suitable molding pressure range are 35～40MPa,40～50MPa and 45～55MPa respectively.By thermogravimetric analyzer simulation analysis for three kinds of aggregate,moisture content is 3.4%,1.9%and 3.4%respectively,the dry conditions are drying 8h,4h and 4h respectively at 110 ℃.We have established the corresponding relation between rheological curve and injection molding process by applying molding process parameter attained with capillary rheometer to the injection molding machine and comparing the mechanical test of samples from rheometer with the injection samples.Experimental results prove that the rheological curve could perfectly guide the process design and adjustment in injection production,that the capillary rheometer and injection process has a great degree of similarity.This is of important guiding significance for analysis and evaluation of raw materials,processing performance,selection of raw materials and the adjustment and formulation of formula.