Fracture Toughness of Discontinuous Long Glass Fiber Reinforced Polypropylene: An Approach Based on a Numerical Prediction of Fiber Orientation in Injection Molding

The fracture toughness of discontinuous long glass fiber reinforced injection-molded polypropylene has been characterized by using the microstructural efficiency concept in combination with a numerical prediction of the fiber orientation during injection molding. The latter was performed by using the SIGMASOFT commercial software. In a three-dimensional numerical scheme, input data such as fiber volume fractions, shear viscosity and mean fiber aspect ratio have been used in order to perform the mold filling analysis. The resulted local fiber orientation parameters for injection molded square plates of long glass fiber reinforced polypropylene allowed to calculate the local fracture toughness with microstructural efficiency concept. The latter were compared with the experimental toughness values obtained by the use of compact tension test specimens. The good correlation between the calculated fracture toughness data and the measured ones shows that a fiber orientation prediction by the SIGMASOFT finite element computer code can be used in combination with the microstructural efficiency concept for the determination of local fracture toughness values in injection molded long glass fiber reinforced thermoplastics. The combined approach opens good opportunities for optimization of a thermoplastic workpiece in its design with respect to local fracture resistance. This will enable the material performance levels to be significantly extended, with consequent increases in engineering applicability.