SMC (sheet molding compound) made of unsaturated polymer resin and other additives reinforced with randomly distributed chopped fiberglass strands has been emerged as a substitute of steel for automotive steel outer body panels because of its weight, stiffness per unit mass, and non-corrosiveness in recent automotive industries. During mold filling and curing stages of compression molding of SMC, the process is non-isothermal since the molding temperature is usually heated to 150℃. Thus, understanding of heat transfer and flow characteristics during fabrication of SMC under various molding conditions is important.
The compression molding of SMC was analyzed based on rigid-viscoplastic approach by three dimensional finite element program. Deformation analysis part of currently developed program was tested by solving three dimensional axi-symmetric compression molding of a cylindrical SMC charge and wedge type specimens of aluminum alloys at various processing conditions. The simulation results were compared well to the simulation results obtained from two dimensional finite element analyses and experimental results available in the literature. Temperature analysis part was tested by solving one dimensional heat transfer problems and compared with the exact solution. Based on these comparisons the program was proved to be valid and was further applied in solving three dimensional compression molding of SMC.
To investigate the effects of friction conditions and mold closing speeds for compression molding of SMC charge at room temperature, compressions of the cylindrical and rectangular shaped SMC were analyzed for various friction conditions and mold closing speeds by using deformation analysis part only, and then by including the temperature analysis and curing analysis parts, the analyses of compression molding of rectangular shaped SMC were carried out for mold temperatures of 130 and 150℃ and mold closing speeds of 15 and 45mm/min to investigate the effect of these conditions on flow pattern of SMC charge and characteristics of curing.
