Analysis On The Influence Of Injection Molding Temperature History On Pc Impact Response

Due to excellent light transmission,high glass transition temperature,high impact toughness,good creep resistance and electrical insulation,the amorphous polymer polycarbonate are widely used in translucent products in aerospace and transportation applications,such as aircraft cockpit windshield,astronaut helmet viewing window and lampshade of high speed train head lamp.Injection molding is the most widely used processing method for polycarbonate.The mold and process parameters determine the final shape of the molded products.In addition,for polycarbonate and other amorphous polymers,injection molding process parameters also have an important effect on the mechanical properties of the injection molded products.The experimental results have shown that the thermal history experienced upon solidification from the melt has an influence on the yield stress of the molded polycarbonate products,which will further affect the mechanical behaviors of the product during its service.In the existing literatures,most of the computation studies of polymer injection molding are focused on how to accurately determine the geometrical deformation of the molded products,but rarely consider the characterization of the material properties after the molding process.Meanwhile,the computational of the mechanical behaviors of polymer products usually neglect the influence of the injection molding process.Motivated by this situation,this study carried out the following two aspects:(1)The influence of the thermal history on the mechanical property(yield stress is considered in this paper)of polycarbonate is studied through experiments.On this basis,the predicting model of the yield stress of polycarbonate from processing thermal history is developed.The uniaxial quasi-static tensile tests of polycarbonate samples with different mold temperatures are carried out to obtain the yield stresses.Numerical simulations of the molding process are performed using MOLDFLOW,a commercial injection molding simulation software,to obtain the thermal history for different processing conditions.The thermal history is then exported to the predicting model to obtain the yield stress from processing.Numerical results are in good agreement with the experimental values and the trend of yield stress versus mold temperature is well covered,which verifies the rationality of the model.(2)A strain rate dependent elasto-plastic constitutive model with the modification to combine the influence of processing thermal history is developed to model the mechanical properties of polycarbonate.An integrative simulation framework which combines the injection molding simulation,evaluation of the yield stress after processing and the finite element computation of the impact behavior is further developed.The Izod impact test of polycarbonate samples with different mold temperatures are carried out.The impact energies of the samples are recorded.Then,the Izod impact behaviors of the samples with different mold temperatures are analyzed by using the integrative simulation framework.Numerical results of the variation of impact energy with mold temperature agree well with the experimental result,which verifies the rationality of the integrative simulation framework.Finally,the effect of mold temperature on the impact energy of the specimen is discussed in details.The research work in this paper provides an alternative idea for the analysis of injection molding and mechanical behavior for engineering polycarbonate products.Traditional injection molding and mechanical behavior analysis are separated from each other.In this paper,an integrated simulation framework of injection moldingyield stress-mechanical response is established,which provides a promising tool for analyzing and optimizing the mechanical behavior of the polycarbonate products from the point view of processing conditions.