Evolution of anisotropy in the mechanical behavior of polymers
A constitutive framework within which to study the plastic behavior of polymers at finite strains is developed in this thesis. Several effects that are known to be significant in the yielding of polymers such as strain induced anisotropy and pressure sensitivity have been neglected in most analyses to date. This is due in part to the lack of certainty as to exactly how these effects should be included. In the present research, a rather simple but flexible means of incorporating strain induced anisotropy and pressure effects as a function of the evolving deformation is developed. The proposed constitutive description is readily incorporated into a flow theory of plasticity or an anisotropic nonlinear theory of elasticity. The anisotropy that develops as a result of molecular orientation is assumed to be orthotropic, with the principal directions of anisotropy taken to coincide with the principal directions of stretch. The assumption of orthotropy is in good agreement with experimental observation. The proposed constitutive models are used to study plane strain necking and plane strain extrusion. ^
Scott David Batterman,
"Evolution of anisotropy in the mechanical behavior of polymers"
(January 1, 1989).
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