Research On Formability Of Carbon Fiber Reinforced Thermoplastic Plastics For Rectangular Thin-wall Plastic Parts

Carbon fiber reinforced thermoplastic resin(CFRTP)material is an indispensable highperformance engineering material in modern industrial and engineering fields.CFRTP material has super high strength and modulus ? low density ? excellent thermal conductivity and electromagnetic shielding.Therefore,it is of great value in the field of new materials.With the rapid development of electronic information?IT?automobile and other industries,the product has gradually formed a style of "light,thin,short,small" design concept.Plastic products,especially the products of 3C(Computer,Communication,ConsumerElectronics),gradually developed to the direction of thin and light.So it is possible to make CFRTP materials are widely used in the "reduction" of 3C products in the field of injection molding.However,it is very necessary to research how to improve the filling performance of CFRTP materials in thin-walled cavity and(to improve)the properties of thin-wall injection molding of CFRTP materials,because the fluidity and filling performance of carbon fiber reinforced thermoplastic resin are poor and the theory of thin-wall injection molding is not perfect.It is important to research that performance of CFRTP material injection molding in rectangular thin wall and to the application of CFRTP material in the field of injection molding of 3C products.This paper mainly studies the injection molding properties of CFRTP materials in rectangular thin-walled parts.Through numerical simulation,the flow performance and forming performance of CFRTP in rectangular thin-walled cavity are analyzed.The ultra-thin notebook shell is selected as an example,and the apparent properties and mechanics of carbon fiber are studied by experiments.The main contents and conclusions are as follows:1)Combining the injection molding theory of rectangular thin-walled cavity,the influence of different cavity thickness on the injection molding properties were researched.The difficulty of forming CFRTP material in thin wall cavity was found.The results showed that the thickness decreases could make cavity injection pressure increased exponentially in the mold cavity,which would make the cavity appear short molding defects,and the defects would become more and more serious with the increase of mass fraction of carbon fiber(CF);Then the injection mold filling of CFRTP in a rectangular thin wall cavity was numerically simulated.The temperature(mold temperature and melt temperature)?the injection rate?the V/P switching point?holding pressure and the curves of different carbon fiber content of the CFRTP materials in different thickness cavities are studied.The effect of injection molding properties.The results show that the increase of V/P switching point and the increase of holding pressure can both improve the warpage and shrinkage rate.2)According to the problem of poor filling of carbon fiber materials,the flow balance of CFRTP material in the cavity is analyzed,and the position and quantity of the material in the cavity of the material and the layout of the gate are studied.The results show that rectangular thin-walled parts should be poured from the front and the number of gates should be increased.Based on the above conclusion,an elliptical "five gates" basic gate layout model is proposed,and the effect of the "five gates" model on the injection molding properties of the melt in a rectangular thin wall cavity is studied.The results show that the "five gate" model can solve the defect in CFRTP filling,and also achieve balanced flow and reduce the inhomogeneity of shrinkage.Based on the flow balance theory and the "five gates" design model,a super thin notebook shell computer in real life is selected as the research object,and an improved version of "five gates" model for the research object is designed.This model is used to solve the problem that the flow front of the CFRTP material is easy to solidify in the ultra-thin notebook shell.The cavity can achieve better balance filling effect.3)The apparent and mechanical properties of the ultra-thin CFRTP notebook shell were studied.Based on the Taguchi orthogonal test and the experimental measurement,the effect of different process parameters on the warpage was obtained.The results showed that the V/P switching point had the greatest influence on the warpage,and the warpage would increase with the increase of fiber content;The effect of process parameters on the shrinkage deformation rate is studied by the experimental design.The result shows that the longitudinal contraction rate along the notebook shell is generally smaller than that in the transverse direction.Using SVG technology,the sequence of gate switching time is designed and the defects of the weld line are solved effectively.The tensile and flexural properties were studied by experiments.The effects of carbon fiber mass fraction on tensile properties and bending properties were mainly studied,and the influence of weld marks on mechanical properties was also studied.The results show that when the carbon fiber mass fraction is from 0 to 20%,the tensile strength and the flexural modulus of the parts increase with the increase of carbon fiber mass fraction.When the carbon fiber mass fraction increased to 25%,the tensile strength and the flexural modulus will show a downward trend.The tensile strength at the weld mark is about 80% to 90%which is without the weld mark.The bending modulus is about 70% to 80%which is without the weld mark.