Affiliations: [a] Department of Mechanical and Industrial Engineering,
220 Roberts Hall, Montana State University, Bozeman, MT 59717, USA | [b] Sandia National Laboratories, P.O. Box 5800, MS-0836,
Albuquerque, NM 87185-0836, USA
Abstract: The paper concerns the dynamic response of polyvinylidene fluoride
(PVDF), a commercially available piezoelectric polymer currently used in
numerous applications. The paper consists of two parts. The first part presents
a summary review of recent experimental results regarding the time-dependent
behavior of PVDF tested under combined static and cyclic loading conditions. It
has been observed that the polymer has demonstrated accelerated creep rates due
to cyclic loading effects. Cyclic creep acceleration in PVDF has been
significant even in the range of stresses well below the viscoelastic linearity
limit. This phenomenon, defined as "vibrocreep", appears to be essentially
nonlinear, since the material response under combined static and cyclic loads
did not represent a simple superposition of the responses to static and fully
reversed cyclic loads applied separately. The second part of the paper provides
a formulation of a nonlinear constitutive model, which describes the
synergistic interaction between creep and cyclic damage evolution. The proposed
constitutive model combines the concepts of linear hereditary viscoelasticity
with damage characterization through a cyclic damage function. The latter is
formulated using the basic principles of continuum damage mechanics. The
potentials and limitations of the proposed constitutive model are discussed,
and experimental results providing model validation are presented.
