Research On Compression Molding Technology Of Hatchback Door Plate With Glass Mat Reinforced Thermoplastics

In recent years, with the growing number of automobiles in the world, the problems ofenvironment and energy consumption caused by automobiles become worsen. People have ahigher request on environmental protection and fuel economy performance of theautomobiles. Therefore, under good automotive performances, automobile lightweight wasused to solve the above two problems. To meet the requirement of automobile lightweight,composite materials appeared and were used widely with the advantages of light weight,high strength, higher corrosion resistance, easiness of manufacture and design flexibility.The paper aims to research on the finite element simulation process of compressionmolding and optimize the molding process parameters based on the application of Glass Matreinforced Thermoplastics (GMT) to a hatchback door plate. Therefore, this paper includesthe following aspects. Firstly, the feasibility of replacement the steel with GMT has beenverified. Secondly, it has been chosen a material model which is suitable for thecharacteristics of GMT and can be used in finite element simulation of compression moldingprocess. Thirdly, the parameters of compression molding process have been optimized.To verify that GMT composite can replace steel, the stiffness and modality ofhatchback door plate with GMT composite were verified to satisfy the design requirement onautomobile covering parts with the method of finite element analysis and comparison withthe test results.There are several material models to choose, which can be used to GMT in compressionmolding processes. Composite material model is a combination of thermal viscoelasticmatrix and elastic fiber. Trims material model is an elastic-plastic material model which cancharacterize the anisotropic and isotropic, and this model contains temperature and strainrate effects on material properties. By comparison, Trims material model which can reflectthe uniaxial tensile process of GMT better was chosen to analyze the simulation ofcompression molding process, and the coefficient of normal anisotropy of GMT was derivedwith parameters reverse method. Finally flat cylindrical part was used to verify that themodel can be applied to GMT.After simulating the compression molding with Trims material model, fourtechnological parameters were found which have great influence on molding quality. They are sheet temperature, mold temperature, punch feed speed and friction coefficient. Finallyradial basis function (RBF) neural network model was used to fit the approximation modelof technological parameters with forming thickness average and standard deviation. ThenNSGA II was used to select a set of process parameters which can get the maximum o fthickness average and the minimum of standard deviation.This paper can provide a scientific method for analyzing the hatchback door’scompression molding and optimizing technological parameters with GMT, and supply ascientific basis for the expansion of GMT application in automotive lightweight as well.