Molecular mechanics simulation on the nanoindentation on POSS nanocomposite

摘要

Mechanical behaviors of the nanoindentation into the films of the polystyrene (PS) and the polyhedral oligomeric silsesquioxane (POSS) reinforced PS (propyl-POSS-PS, P-POSS-PS) were studied using the molecular mechanics simulations. The serrated load-displacement curves of two kinds of polymers were obtained. And the curves show that the loads increase with increasing displacements. A method to compute the hardness of homopolymers in the molecular simulations of the nanoindentation was proposed by considering the response of the load-indentation depth and the constructional deformations of the simulation models. The results indicate that the hardness of the P-POSS-PS (9.1mol% propyl-POSS attached) is about 60% higher than that of the PS. The hardness of polymers can be observably improved by the POSS. A formula is deduced to characterize the relationship between the hardness and the indentation depth of common polymeric materials based on a kind of representative polymer nylon. Computational results prove that this formula is valid to a large proportional of polymers. Afterward the hardness of the PS and the P-POSS-PS were corrected and the necessary indentation depths for the credible hardness were provided.