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Multiaxial nonlinear viscoelasticity of solid polymers
Author(s) -
Buckley C. P.
Publication year - 1987
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760270210
Subject(s) - viscoelasticity , isotropy , materials science , creep , compressibility , nonlinear system , stress (linguistics) , hydrostatic equilibrium , deformation (meteorology) , symmetry (geometry) , mechanics , composite material , mathematics , geometry , physics , optics , linguistics , philosophy , quantum mechanics
A scheme is presented for characterizing multiaxial nonlinear viscoelasticity of solid polymers in a manner suitable for application to the prediction of deformation of polymeric parts. The basis of the scheme is the systematic exploitation of simplifications resulting from: (1) restrictions on the class of stress histories considered, (2) material symmetry (e.g., isotropy), and (3) the nature of viscoelastic nonlinearity in any given material. Several classes of stress history are considered. In the special case of inplane response of an isotropic material to a two‐dimensional proportional loading history, it is shown that the nonlinearity can be expressed through the dependences of compressibility B and shear compliance J on two invariants of the stress history: I 1 and I 2 ′, which separately characterize the magnitudes of hydrostatic and deviatoric components of the stress tensor. When this approach is applied to the description of biaxial creep and recovery of isotropic polypropylene, it is found that for strains up to 0.012, B is independent of I 1 and I 2 ′, while J is linearly related to I 1 and I 2 ′. These results are used to predict axial strain and hoop strain in the wall of a pressurized pipe, and the predictions compared with those obtained with three approximate procedures.