Examples of creep and creep recovery curves of polypropylene (PP) samples are shown in Fig.
The TWCS method can be adapted for performing creep, creep recovery, and stress relaxation tests.
According to the results of the study as shown in these figures, the instantaneous creep recovery
was approximately equal to 50 percent of the magnitude of the instantaneous elastic deformation for red oak and yellow-poplar shelves.
Based on the recommendations, the time and strain data from the 50th and 51th cycles of the repeated creep recovery
test were fitted to the four-element Burgers model as shown in Eq.
A property closely linked to creep recovery is stress relaxation and the residual stress build-up in thermoformed parts can be correlated with the characteristic stress relaxation time ([[lambda].
The tests included dynamic temperature sweep tests, dynamic frequency sweep tests, creep, and creep recovery tests.
The model with one Kelvin-Voight element is enough to fit adequately the creep and creep recovery of the materials for short-term tests.
The agreement of the experimental data from creep recovery and dynamic mechanical tests with the calculated values shows that the Burgers model including a distribution of relaxation times is a simple but powerful tool to represent the viscoelastic response of the polymer and composites studied.
experiments were performed on the same instrument.
omega]), and the creep and creep recovery
functions of the blends were measured in a tension controlled rheometer SR-200 also from Rheometrics, at 290[decrees]C, using a parallel plate geometry, under nitrogen atmosphere.
An alternative function that has been successfully used to describe the creep of predominantly semicrystalline polymers (4) is based on the Williams-Watts model for describing charge decay in dielectrics (8) and is consistent with the creep recovery
function exp - [(t/[Tau].
1]) the load is removed and the creep recovery
response is given by: