Characterization and simulation of impact behavior of graphene/polypropylene nanocomposites using a novel strain rate–dependent micromechanics model

Abstract

The current paper examines a newly developed model to simulate the strain rate–dependent constitutive equation of graphene/polypropylene nanocomposites. The model is a combination of the Halpin-Tsai micromechanics method and the Goldberg model which is called the strain rate–dependent micromechanics model. First, tensile properties of pure polypropylene are measured experimentally. Then by utilizing the Halpin-Tsai micromechanics method, tensile properties of graphene/polypropylene nanocomposites under static loading conditions are achieved. The obtained properties from the micromechanics method are used by the Goldberg model in order to simulate the strain rate–dependent mechanical behavior of nanocomposites under dynamic loading conditions. The material constants of the Johnson-Cook material model are calculated by the strain rate–dependent micromechanics model. The material constants are used in a material model which is implemented in the explicit finite element code LS-DYNA, to simulate the strain rate strain rate–dependent micromechanics-dependent mechanical behavior of the standard Charpy impact test specimen. Polypropylene reinforced with 0.5, 1.0 and 2.0 wt% graphene sheets were prepared via coating polypropylene with graphene particles. Then, by melt blending in a twin-screw extruder followed by an injection molding process, the nanocomposites samples are manufactured. The results revealed that the incorporation of a low amount of graphene caused a good improvement in impact strength of polypropylene. To evaluate the current model, the results are compared with the experimental results of the standard Charpy test specimens. A good agreement between the experimental data and the strain rate–dependent micromechanics model is achieved.