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.

Date Published: 1 November 2007
PDF: 6 pages
Proc. SPIE 6423, International Conference on Smart Materials and Nanotechnology in Engineering, 642322 (1 November 2007);

Published in SPIE Proceedings Vol. 6423:
International Conference on Smart Materials and Nanotechnology in Engineering
Shanyi Du; Jinsong Leng; Anand K. Asundi, Editor(s)