Simulation of compression molding for sheet molding compound considering the anisotropic effect

An improved model of the anisotropic flow characteristics of SMC (sheet mol ding compound) during compression molding is developed. This study is inten ded to complement our previous paper, which was conducted to determine the anisotropic parameters for short fiber reinforced thermosets SMC (16). Our prior study measured flow viscosities and material anisotropy by means of a xisymmetric and plane strain compression molding tests. The current study, in order to identify the superior flow model from the choices 1) isotropic, 2) constant anisotropic and 3) varying anisotropic, applies the finite ele ment method to obtain numerical results, which are subsequently compared wi th experimental results to determine the flow model with the best fit. The anisotropic parameters of the shear directions are determined by use of nor mal and planar parameters because SMC is planar isotropic. Six varying anis otropic parameters and six viscosity values are estimated during molding ex periments, which are conducted at room temperature so that the polymer does not cure. Two-dimensional molding numerical analyses are carried out to ex plain two experimental classes, axisymmetric and plane strain compression m olding. The load-levels predicted by the isotropic model, anisotropic model (parameter values fixed) and anisotropic model (parameter values varying) are compared with the experimentally derived values, the results showing th at the varying anisotropic model best fits SMC compression behavior.