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In this paper,the nanoindentation simulation on the two models of neat polyethylene (PE) and the polyethylene incorporated with 25wt％ POSS (POSS-PE) is performed to reveal the reinforcing mechanism of the mechanical properties.The influence of the indenter shapes on nanoindentation is researched by using three different shapes of diamond indenters (cube-corner indenter,cylindrical indenter with spherical tip and cylindrical indenter with fiat tip).The molecular mechanics method is adopted to eliminate the temperature effects.Under different indenters,the load-displacement responses,hardnesses (indentation hardness and Martens hardness) and Youngs moduli of PE and POSS-PE are obtained.Compared with PE,all the mechanical properties are improved dramatically.Then,we analyze the source of loading drop phenomena and the enhancement mechanism of POSS.Furthermore,the result shows that the different shapes of indenters cause a large impact on indentation hardness,but a little impact on Martens hardness.And Youngs modulus of the fiat indenter is much larger than that of cube-corner indenter and spherical indenter.