Modelling of Deformation Behavior of Micro-Mezo-Macroscopic Scale of Glassy Polymers

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In the development of a constitutive model of deformation behavior for a glassy polymer, molecular chain network theories have been developed to take account of the strain-induced anisotropy due to the alignment of the molecular chains and the changes in the number of entangled points. However, the suitable constitutive equation which can duplicate the general deformation behavior of polymeric materials and relationship betweenn the micro-and macroscopic behaviors of polymeric materials, that have hierarchical structures at successive molecular to macrolevels, have not been clarified vet.In this work, a new molecular chain network model, nonaffine model, which allows the change in the number of entangled points due to the thermal activation caused by the temperature change and the pullout of the molecular chain from the entangled points by local deformation. An identification method employing both experiments and computational simulation has been developed and thus established constitu … More tive equation has been approved through the computational prediction of experimental results. Furthermore, the peculiar instability propagation behavior observed in the tensile deformation as well as in the shear deformation under different deformation conditions.Next, in order to estabish the hierarchical constitutive model covering the response of molecular structure of mononer leading to deformation on a mezzo-and macroscopic deformation behavior, we applied AFM and clarified the relationship between the micro-and macroscopic behaviors. For highly oriented ultrahigh molecular weight polyethylene, (UHMW-PE), hierarchical structures with scales from microns to angstroms were observed such as microfibril structure aligned along the drawing direction, and nanofibril structure with dozens of nanometers. On the molecular level, regular chain pattern is formed on the surface of the nanofibril structure. The observation of microscopic surface profiles of PC,a glassy polymer, under uniaxial tension with neck propagation has clarified that the formation of microfibril structures aligned along the tensile direction on the surface and the clear delay in the rotation of aligned microfibril structures with rsepect to that of principal direction of plastic stretch due to shear strain, which suggests the necessity of the establishment of the nonassociative frame work for the constitutive equation. Less