Impact of viscoelasticity on the stiffness of polymer nanocomposites: insights from experimental and micromechanical model approaches

The mechanical properties of BaTiO3 filled HDPE nanocomposites are studied by experimental and numerical approaches. First, the viscoelastic behavior of neat HDPE is highlighted experimentally in tensile and relaxation tests. A method is then proposed to define a constitutive viscoelastic law representative of this behavior at different tensile crosshead speeds at room temperature. Afterward, this law is implemented in a finite-element-based micromechanical model representing the BaTiO3 filled HDPE nanocomposites with different filler amounts. The experimental and numerical results are further compared. Both the experiments and numerical simulations confirm the viscoelastic behavior of the polymer nanocomposite. For nanocomposites with filler concentrations up to 20%, the error between the experimental and numerical findings remains less than 8%, confirming that the model represents well the composite behavior for low and moderate filler amounts. The proposed strategy can be applied to other polymer composites in order to predict the complete mechanical behavior of viscoelastic composite materials.