Orientation hardening amorphous

In the case of the amorphous phase one may only consider the influence of the inelastic deformation on molecular chain rotations and the subsequent strain hardening effects. The initial texture and pre-orientation effect can be considered by the segmental rotation resistance and network stretching resistance. It is common to neglect the texture effect in elastic deformation and consider it only during inelastic deformation. Dupaix and Boyce [100] relate the initial values of the back stress tensor, a,y, athermal shear resistance, s, network stretch... 

In an isotropic polycrystalline polymer whose microstructure consists of stacked lamellae arranged in the form of spherolites, the slip systems activated depend on the local orientation of the lamellae with respect to the applied stress and, as deformation proceeds, these orientations are modified. To calculate the evolution of the crystalline texture, one can consider the polymer to behave as a crystalline aggregate. Although the entropic contribution of chain orientation in the amorphous regions may also need to be considered, the major contribution to work hardening in tension is rotation of the slip planes toward the tensile axis, so that the resolved shear stress in the slip direction diminishes. This results in a fiber texture in the limit of large deformations, such that the crystallites are oriented with their c axis (the chain axis) parallel to the stretch direction. Despite the relative success of such models, they do not explicitly address the micro-mechanisms involved in the transformation of the spherulitic texture into a fiber texture. One possibility is that the... 

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