Simulation of compression molding of long‐glass‐fiber‐reinforced thermoplastic sheets

Abstract An isothermal two‐dimensional shear‐thinning model of the compression molding of long‐glass‐fiber–reinforced thermoplastic is presented. A transverse isotropic behavior is introduced by considering two different pairs of power‐law coefficients. First ( K ₁ , m ₁ ) is linked to the shear deformations through the thickness and to the compression deformation; second ( K ₂ , m ₂ ) is associated to the expansion motions in the plane. K ₂ is significantly greater than K ₁ because of the influence of the glass mat structure, which resists stretching in the plane of the part. These coefficients are determined by fitting the computed and experimental mold closing forces in a circular isothermal compression‐molding test. The average velocity through the thickness is obtained by a variational method. Incompressibility is ensured by penalization. A finite element method is used, with a convected mesh and remeshing technique. The agreement between this model and experimental results (shape of the sample, mold closing force, pressure) performed on a rectangular mold is good.